You can credit a BA operated flight to Advantage if it's booked under another Oneworld partner. For instance, last year, when Canadian was still part of OW, i flew LHR-YUL on a BA plane but under a Canadian Airlines number and it went to my AA account without problem, with the double miles due to Platinum and flying a OW airline.
Unfortunaly, BA in the Americas, doesn't codeshare anything but the London -Santiago de Chile with Lan Chile.