Originally Posted by
PLeblond
I would add that in case of IRROPs, and assuming you are leaving out of LHR, AC would provide more rebooking options. BA does not have a OW partner in Canada and being rerouted via the US would add a lot of immigration steps, most especially if travelling with a checked bag.
However, as YVR is a preclearance airport immigration is handled before leaving Canada and any bag will be checked through to the final destination without claiming and rechecking in the US.