My experience is that whenever AA helps out with a problem on a BA ticket, BA refuses to help out and denies the claim. After a lot of back-and-forth emailing BA (you cannot speak to anyone), the last comment on my case was 'waiting for information from AA'. To date, no refund for a downgrade has been received and I don't think I will ever receive anything after five months. I looked at CEDR but I can't work out how my complaint fits in, as we ultimately arrived at LHR on AA. Decided to take my business elsewhere in the future.