I'm currently in the preliminary research stages for a story set in my home region of Northern Alberta. Specifically, it's going to be set in Fort Chipewyan. Recent events have suggested to me that while Fort McMurray wouldn't survive the apocalypse, Fort Chip might very well pull through.
They have isolation on their side: the only way to get there is by water, air, or the winter ice road, which can only be used between mid December and early March. Not to mention, they're completely surrounded by forest, and have cold winters, short summers, and a population used to being at least somewhat self-reliant.
The population is primarily Chipewyan people, so there is zero doubt in my mind that in this scenario, traditional beliefs would make up their spirituality/magic system. (But unfortunately, I don't know much about Chipewyan/Dene beliefs, so this is one area where I'll have to research a lot.)
Communication with other areas would be difficult, because of how spread out everything is up here, but I do think that they would find some way to contact other populated areas - which, again, would mainly be isolated reservations (or rather, former reservations) like Fort Chipewyan itself. The Athabasca River system could be used for transport, but there are some parts of it that would make travel very difficult - mainly the fact that it passes directly through Fort McMurray, so anyone navigating in that direction would have to deal with trolls and rapids.
I'm kind of toying with the idea that, by Y90, they would have formed some sort of collective Athabascan trade alliance with the other populated areas. But it's something I need to think about more.
Because of the level of isolation, and the spread-out population, these people would be living in a very low-tech way. The early years would have been very, very hard. (As comparison - even Finland would probably have more resources available, or failing that, at least more places to loot from). So, traditional knowledge - both practical and spiritual wisdom - would be utterly crucial in all respects.
Unfortunately, our library has only just re-opened this week, so I haven't had a good chance to read up on things and develop these ideas in detail. But soon... < 3