It doesn't matter if they do or not... they still have to issue the ticket on whoever prices the ticket. And in the case of many parts of former 'eastern' europe, that responsibility lies with BA and not AA as most TAs in Europe do not have any ticketing rights with AA.

There is a very convuloted way in which one can get AA involved in pricing the ticket and forcing BA to honor the fare quoted by AA in USD instead of EUR to issue the ticket as is, but it would involve AA in the US, Dublin, Thailand and whatever EU country you want the ticket issued from..

I'll try it later in the year.. and if I succeed, I'll share it. But in the meantime..