You would need to contact AA for any refund

If it was an AA fare, then AA's conditions of carriage apply ; if a BA one then AA would just be acting as an agent and so BA's conditions apply

Both BA and AA state that the cancellation penalty is

Unless you have a ticket which is refundable minus a penalty less than any insurance excess or change fee is less than the excess, the easiest method would seem to be to contact the travel insurer