Thank you all for your feedback.
It sounds like, as with many things on this forum, "It Depends"
And it is probably spotty at best.
While watching these reply's come in, I did further research, finding similar results across the board. With some folks reporting coverage way up in Inivik and on the North Slope, and others saying it died south of the Yukon/BC border. Interestingly, when I called both Sirius.com and Sirius.ca, I got different stories. Sirius.com says there is no coverage in N. Canada and Sirius.ca says they cover most of YT (specifically, she said that they cover both Whitehorse and Dawson City). Perhaps they use different satellites????? However, both clearly said there was "no coverage in Alaska" (somehow the signal that "works well" in Whitehorse magically knows where the Alaska border is.......).
It does seem like a roll of the dice, though one major theme seems to be a good quality antenna, mounted as high as possible, with the best possible view of the S/SE sky.
As to what I am going to do (do I purchase the equipment and sign up for service or not?), the jury is still out. We enjoy listening to talk radio in the evenings (no TV along) and it's tough to get the programming we enjoy with the shortwave receiver.
Anyway, thanks again all. If someone has something else of value to contribute, I would enjoy hearing it.