Originally Posted by
BA6501
Not quite - IB's rules apply in this case, so one bag comes free (not sure about Bronze - I think just the IB equivalent gets that). Things were a bit odd back in the BA operated by IB operated by BA days on the LHR-MAD route, but that's long gone.
Try logging in to BA.com with your Gold, Silver, or Bronze card and enter a dummy booking selecting BA marketed, IB operated flights. With BA marketed Basic fares, there is no special baggage allowance for oneworld Emerald, Sapphire, or Ruby card holders. If you book an IB marketed ticket then the outcome is different.