I was op-upped once on a CPT>LHR flight from World Traveler to World Traveler Plus. This was only because a family was throwing a fit about not being able to sit together, and I had the aisle row in the row where four of the five family members were seated. It was a full flight, so they couldn't ask me to move to another aisle seat in WT, and I would have told them to f-off if they had asked me to take a center seat.
Other than a peculiar situation like that, I think there is zero chance of an AA elite getting an op-upgrade on BA. They don't even qualify you for an exit row seat.