The BA website for booking class C has the footnote: "1 This class may award at the rate of 100% of the flown miles when used for upgrade purposes." Implying that you earn as per the underlying economy base fare of 100% miles. Granted that isn't totally clear as to TP earning.
Unless they re-issue your ticket, you are still booked in your original fare code but travel in class C.
Just had mine post as the following:
NEW YORK-JOHN F KENNEDY - ZURICH (Y/C)
AA64(Operated by: American Airlines)
So, no extra for the AUP, which is a bit of a downer. OTOH, this was part of my re-route, so I got the points for my original route. In the end, I'm 10 TP from my renewal on the Bronze. I did have to call to get them to post. Still waiting for Mrs. greg5's account to post. Sadly, the other leg of the re-route was on DL, so I'll just have to put that on the ASA account.
But, I do find it quite unclear on the BAEC website as far as the TP go.