Holbiho, why do you think AA's rules apply to your BA flight?

I can give you another example of operating carrier rules prevailing... PSC-SEA-DFW. PSC-SEA is an AA codeshare on QX (AS). SEA-DFW is on AA. If you check luggage DFW-PSC, it's free as an elite. If you check luggage from PSC-DFW, you pay AS's rates. This is a pretty well known fact on Flyertalk.