You'll have to try convince BA to uncredit the miles/TPs and then retrospectively claim them with AS. It might happen, it might not.

I believe that changes made to bookings on the day like FF numbers are made in FLY (the software BA use at the airport), which means it's only really updating the flight that is under FLY's control.

Obviously hindsight is 20/20 however your best bet is to try and change it before you fly.