Originally Posted by Fiordland

It is up to CX. If they are willing to tag you bag all the way then your good to go. Given AA, WS and CX interline it can be done. Where you run into problems, is some airlines are starting to refuse to check bags unless on the same ticket. When this happens it is not because they can't its is because they don't want to.

If the bags are tagged all the way, I would surprised is WS charged you anything.

In Toronto in Terminal 1 bags are automatically transferred behind the seen as you go through customers. Similar to Europe. I don't believe Terminal 3 (used by WS and AA) is setup to operate that way and you will likely have to pickup your bag. There should be a WestJet transfer desk and a connecting baggage drop off.