Even so, a good point is being made here - would doing a soft landing and heading back to the assistant prof job be an option? Unless you land a comparable job in Canada. Maybe not be an option (I know of places where assistant profs are always untenured and have their contracts fail to get renewed for all kinds of reasons outside of their control) but if it is...
I mean, of course you can always try walking into a mcdonalds, starbucks, loblaws... lots of high turnover minimum wage part time retail jobs available. Most likely you'd end up taking multiple in order to make ends meet. I don't think I need to point out the obvious downsides here (including that you might not get the time to apply for proper roles - they say one should treat looking for a job like a full-time job)
I agree with this - assuming it's still possible. (Enough time has gone by that perhaps the spouse in the home country has already left the post and it's already been filled; there might be no going back. And that assumes it was even an option - perhaps the timing of that spouse coming now to join the one already in Canada is because of layoffs or department closing down, etc - so staying was never an option.)
Conversely, if the option truly is closed (though neither person on the account has confirmed this AFAIK) bring it up is probably not helpful - it would no longer point to a way forward.
Assuming the spouse in the home country can't keep the job there or find another, the best way is to try to network and find a similar post in Canada. I don't know too much about professorship or academia and have no idea if this is feasible or not, but it's the best option for the spouse newly arriving in Canada. It's easy enough to find a survival job - just google for Tim Hortons or Loblaws hirings and apply, someone will get back to you - but once stuck in there you might have a more difficult time getting out.