I have booked a LAX-LHR on BA economy (but identified as basic economy when going through the purchase process) later this year. In my situation, I am paying less USD, but will get more EQD and EQM. The tradeoff is not being eligible for upgrades or applying a SWU.
The key here is to see what fare class the BA codeshare flight on AA metal is. The OW benefit for seat assignment applies, and you will be able to select a MCE seat with BA at booking. You may need to call in to accomplish this. In addition, the AA itinerary will appear on your AA profile, but you will not be able to change a seat assignment on AA without paying a fee. All changes would have to be done through BA.
Last edited by tbone14; Aug 1, 2019 at 2:32 pm