I'm pretty sure that the comics (post-war) had to have new printings in Canada rather than shipping the product across the border into Canada. I think Bell mainly survived by being a press--aside from the comics, they put out other books, as well.
I'm almost certain of this simply because the quality of the printings in Canada was worse than the American version--with pages printed incredibly off register in some issues. You can also tell that it's a different paper stock.
It's possible that some of the Canadian companies just put a new cover on American material (or British material)--that likely did happen--but the regulations at the time maintained that the material had to be printed in Canada.
Later on, with other regulations which mainly applied to magazines like TIME, the Americans supplied the material for distribution in Canada, with added Canadian content.
Oh Canada, we stand on guard for our cultural identity.