I will let you know what happens for me. I bought the upgrade offer for my last AA flight. It changed the booking class on my boarding pass to C, which on the BA website carries the footnote:
These classes may award at the rate of 100% of the flown miles when used for upgrade purposes.
Which makes me think that I'll only get the TPs and Avios I would have gotten had I flown in my originally booked class of service. (
source)