For reference, their most up to date TA schedule change policy (https://www.aircanada.com/content/da...KCH_EN_V16.pdf) says "for Transatlantic, Transpacific and South America, the order of protection for using other carriers is only as last option, if no AC over-the-water flights are available"

I could argue there are no AC over-the-water flights available from BCN, but I'm not really keen on spending hours on the phone.