Nearly all oneworld benefits apply to flights marked and operated by a oneworld member (or affiliate). AA*/B6 flights are not operated by a oneworld member or affiliate, so I think it unlikely that BA elite benefits would transfer over, though I have no relevant experience. (Certainly they don't have to by the letter of oneworld rules.) Bilateral agreements like the one between AA and B6 don't transfer to other oneworld frequent flyer programs.
There are some exceptions to this general rule (eg AA members at least used to be able to earn elite-qualifying miles on QF*/EK flights even though EK is not a oneworld member), but they're fairly rare.