Note the idea was joining Canada as-is, or forming a "Cascadia". I think the latter is much much less realistic myself :)
I sure as heck wouldn't want B.C. or any Canadian province to split off from Canada.
EDIT: I think you're absolutely correct that separatists ignore their own region's dependencies on the parent state. Quebec, for example. The separatists there always hand-wave away the question of how they would deal with losing access to the rest of Canada's resources (physical, cultural, economic and political).
May's definitely not a Russian asset. She just has a good sense of humour.