In the situation you describe, if somebody is subject to a custodial sentence, they don't hang around. Historically, CBSA has prioritized people who are serving criminal sentences because, frankly, they're easy to find. They don't get released. They often end up being put immediately into immigration detention, which may or may not be, in fact, in a jail or a detention centre.
Actually, they are the people who are probably most likely to be deported.