Just a note that GV doesn't actually care about your IP address, or anything like that, so one wouldn't have to be outside of the US to see whether any of these types of numbers would successfully register an account. So if anyone wants to try that step, feel free!

The issue I've found is successfully getting a number that GV will accept, since some of these common services people use either cannot be registered in Canada or GV is on to them. For example, we have a Skype-In US-based number (since there's no Cdn Skype-In service) but GV won't allow that number as a registered number.

So there may very well be a particular service or configuration that I haven't yet found that will in fact work, but at some point I realized I don't really like talking on the phone anyway, and while it was cool to play around and use free services to create a wifi phone (Grand Central & SIP number on my N810, for example), I'm much less interested in a solution that costs money, given I simply won't use it. I just like the challenge of getting it to work.