If you can get YUL to tag the bags to YVR, then they shouldn't even be placed on the baggage claim belt at YYZ and there shouldn't be an issue. The problem is getting them tagged right through to YVR. Most AC and Jazz agents will resist doing that as described above.

I don't know what happens if the bags are tagged to YYZ, but you decide not to pick them up at the YYZ baggage claim right away and leave them until morning. I'm not sure I'd want to run the risk of trying to find them at 5am.