A lot of companies do that already

However, it's not as simple as it seems, you think "let's send everybody to Canada and then grow our offices there with all the foreigners we want" but that doesn't happen and you wonder why.

Maybe they don't want to outgrow their main offices, or maybe it's got to do with Canadian work culture

I've seen people being "parked" in Ireland before applying for their H1B

It seems to be quite common with movie visual effects companies. And the Toronto or Vancouver offices are often bigger than the LA staffs.

Of course, that industry is being priced down to survival levels.

That's partly related to the non CGI parts of movies often being shot in Canada because of cost advantages. In Toronto you couldn't walk two blocks without tripping over a film crew.

Snow.