Does anyone know if there is any available information as to how the sites were sorted out (like we previously had for the Netherlands, UK, Germany and Switzerland)?
Interestingly, only natural and indigenous sites were chosen (and one technical).

There are 2 stages in "sorting out" the sites
a. Acquiring suggestions
b. Determining which will be selected.
The Parks Canada site does explain in outline how each of these operated
"A public process was used to solicit applications for consideration for Canada's Tentative List for World Heritage Sites. 42 applications were received for sites from across the country, and reviewed by an independent Ministerial Advisory Committee of Canadian experts in the fields of natural and cultural heritage. The Advisory Committee recommended to the Minister of Environment and Climate Change and Minister responsible for Parks Canada the addition to the Tentative List of those properties with strong potential for successful inscription as World Heritage Sites."
For the Committee members see
https://www.pc.gc.ca/en/culture/spm-whs/indicative-tentative/b

What we seem to be "missing" is any report from that Committee as to exactly HOW they determined "strong potential" - the equivalent UK Committee for instance produced a report which contained their reasoning. I have found here a document describing the "Application Process" for anyone wanting to propose a site (together with necessary background and the timetable - which has been adhered to!)
http://www.pc.gc.ca/en/progs/spm-whs/sec06/~/media/progs/spm-whs/pdf/Canada_s_Tentati ve_List_for_WHS_Information_Document-ENG.ashx

But I can find nothing regarding their reasoning in making their selection. So, I have used the "contact us" e-mail address to ask them if they intend doing so in what is supposed to be an "open process" (whilst referring to the document in which the UK Committee had published its conclusions!). It will be interesting to see what their response is (if any!).

I am surprised by the absence of a Salish Sea nomination. There seemed to be a strong coalition of organizations campaigning for its candidature.

I've tried to summarize the Canadian (combined) Tentative. Of the 14 nominations, eleven nominations have criteria based on indigenous cultures. There is also a concerted effort to nominate mixed sites and cultural landscapes. Of the 14 nominations, nine come from 3 provinces: British Columbia (3), Nunavut (3), and Yukon (3).

British Columbia
- Hecate Strait and Queen Charlotte Sound Glass Sponge Reefs (Natural)
- Stein Valley (Cultural Landscape)

Newfoundland and Labrador
- Heart's Content Cable Station Provincial Historic Site (Cultural)

Nunavut
- Qajartalik (Cultural)
- Sirmilik National Park and the proposed Tallurutiup Imanga National Marine Conservation Area (Mixed)

Québec
- Anticosti Island (Natural)

Saskatchewan
- Wanuskewin Heritage Park (Cultural)

Yukon
- Yukon Ice Patches (Cultural)


Remaining Tentative Nominations (6)
- Manitoba/Ontario - Pimachiowin Aki (Mixed - 2018)
- Yukon - Tr'ondëk-Klondike (Cultural Landscape - 2018)
- Alberta - Writing-on-Stone / Áísínai'pi (Cultural - 2019)

British Columbia
- Gwaii Haanas (Mixed)

Nunavut
- Quttinirpaaq (Mixed)

Yukon
- Ivvavik / Vuntut / Herschel Island (Qikiqtaruk) (Mixed)

I find this tendency no less than striking. No other ex-colonial state shows a similar percetage of indiginous TWHS. I think no single Latin American country has such a focus in its T list with the exception of Peru (4 out of 7 TWHS).

It's an example I hope the United States will follow in the next tentative list update (2025?).

The US has 6 WHS sites based fully or in part on indigenous cultures. Canada has only 2, so its a reasonable assertion that Canada is rather late in nominating indigenous sites. However, what's most striking is Canada's approach regarding "living" Indigenous cultures and how many of these nominations are organized as mixed sites or cultural landscapes. There are several Native American sites in the United States that could benefit and ultimately be inscribed if a similar approach was taken.

In the coming years, the US will have been successful in large-part in inscribing tangible remains of Puebloan and Mound-builder cultures. What is next? Black Hills Cultural Landscape? Canyon de Chelly National Monument (mixed)? Ancestral Sites of the Dine (cultural landscape)? Sinagua Cultural Landscape? First Peoples Buffalo Jump (cultural)? Coso Rock Art District (cultural landscape)? There is at least a dozen indigenous cultural legacies or living heritages throughout the US that could fall into the cultural landscape or mixed nomination criteria and reach inscription.

I noticed these 2 nominations have not been updated. Both nominations replace previous versions and both links no longer work on this website.

Tehuacán-Cuicatlán Valley: originary habitat of Mesoamerica (Mexico) 2017
Writing-on-Stone / Áísínai'pi (Canada) 2014

I have received a quick and courteous reply from Parks Canada.
They didn't offer any information regarding the detailed comparisons between those sites which have been selected for the new T List and those which have been "parked" or rejected. They merely referred to the info which we had already seen which contains the "values" which the 8 selected sites are considered to possess -
https://www.pc.gc.ca/en/culture/spm-whs/indicative-tentative

To summarise
Hecate - viii, ix, x
Stein - iii, vi
Wanaskewin - iii
Anticosti - viii
Heart's Content - ii, iv
Qajartelik - iii
Sirmilik - v, ix
Yukon Ice - iii, v

Fixed! Thanks.
Tehuacán-Cuicatlán has gone from a natural site to a mixed site in the process, so it seems

So which are the countries which have a truly transparent procedure of nominatig TWHS? I can recall the following countries: UK, Germany, the Netherlands, Ireland and Switzerland. What about the US? Any documents with their reasoning? Any other countries?

Assif

The topic US approach to World Heritage covers some of the US procedure. Solivagant posted a US ICOMOS report earlier this year which talked about the gaps in the World Heritage list the US is trying to fill. During the period in which the US was updating their list, they were also accepting public comments. The criteria, justification, and comparisons for each of the tentative sites has also been posted to the UNESCO website. Does this help?

This would add the USA to the list of countries following a transparent selection procedure.
It is interesing to see that many democratic countries do not publically anounce how their selection is made. This is true for example of all Scandinavian countries otherwise well known for their governmental transparency.

Busan Provisional Capital and Refugee Trail (Korea)

Officially selected and approved by the Cultural Heritage Administration of Korea. A serial nomination of 14 sites and the first modern heritage nomination from South Korea. It should be added in the "first half of this year" with the aim of inscription in the year 2025 (75th anniversary).

http://news.joins.com/article/22266219

http://world.kbs.co.kr/korean/news/news_Cu_detail.htm?No=297868&id=Cu

http://www.newsis.com/view/?id=NISX20180108_0000196690

Removed from Mali Tentative List
Le Kamablon, Case sacrée de Kéniero (2017)
Le site culturel et naturel de l'Arche de Kamandjan (2017)
Le site de Kurukan Fuga (2009)

I don't understand why 1 year old nominations would be removed from a tentative list, but so it seems.

They are all a part of the new serial nomination:
Sites historiques et paysages culturels du Manden (08/01/2018) (Mali)
http://whc.unesco.org/en/tentativelists/6280/
This used to be a serial nomination "Etablissements humains de la region de Kangaba, coeur du Pays Mande", then it was separated to its four components and now they are trying the serial approach once again.