The vast majority of my travels are done using a single airline (either AC or UA) for the entire journey. When I do "interline" it is normally from an AC flight to an AC codeshare flight (so for any changes, etc. I'm only ever dealing with AC).

I've recently had to book a few interline tickets. A trip I recently completed to YYE involved interlining on both the outbound and return YEG(AC)YVR(9M)YYE(9M)YVR(AC)YEG. I've got another trip (this time to the US) in a few weeks with AC on the outbound and DL on the return (I had to book DL as they had the last flight out that day). In both cases a single ticket was issued on 014 ticket stock and the individual fare components are non-refundable.

So, my question is what happens with any fare credit on an interline ticket should I have to cancel my trip? Say the base fare for the AC component is $250 and the base fare for the other airline's component is $250. Would I end up with separate credits of $250 on AC and $250 on the other airline (both of course being subject to change fees, etc. with "most restrictive applying to the entire ticket"), or would I end up with a single credit of $500 on AC (since this is 014 ticket stock)? Would something different happen? Does it matter if I use AC and connect to the other airline enroute to my destination (and return) vs. using different airlnes for the outbound and return portions?

There is a very good chance that I'll have to cancel my upcoming trip and I just wanted to do a bit of research before talking to the TA should the cancellation be necessary.