Originally Posted by
Often1
1. It was the responsibility of AC to rebook OP on the "day of". If AC did not book the proper fare basis to include a luggage allowance, that is between OP and AC. A chargeback against BA for charging a fee BA is entitled to charge, will be denied and just wastes time, effort and money. OP will need to recover the bag fees from AC.
2. If there is EC 261/2004 compensation due, it is due from AC, the operating carrier of the segment causing the delay. Whether there is compensation due will depend on the length of the ultimate scheduled delay at OP's destination, e.g. YVR. OP needs to supply that information. It would appear from the flight information that the AC cancellation was due to a mechanical issue, thus likely compensable.
Note that the EC 261/2004 claim is separate from the bag fee issue. OP has two claims to make (depending on the length of the delay into YVR) and they must be separately made. Combining them will delay and make this harder.
If he was re-routed onto BA - BA has to accept his original ticket terms and also needs to accept it at face value per the IATA rules. What I have read (and I'm sure it's much more complicated) is that if you have "zero fare" because of a points ticket - the original carrier needs to compensate at the full fare level. However - perhaps the assigning airline can "purchase" another fare. As the cheapest fare probably was one which did not allow bags, it sounds like a refund issue you should take up with Air Canada.
If you have a chance - can you do a lookup of your ticket number from your BA boarding pass on the Saudia website and see what your fare category is as well as your baggage allowance. That should show you what AC had done to get your space.