I could be wrong but its my understanding for mileage crediting purposes it goes by the owned and operated by flight number and not the codeshare flight numbers. So if the BA flight number is within the allowable BA flight #'s then you should get credit.
That was my impression as well, and had previously gotten credit on the same flight from a previous booking. The reason I'm unsure is that I submitted it for credit a few weeks ago and got no answer. I forwarded it (resubmitted) again last week as it was well past the 12-14 business days and didn't get a reply or credit.
Heck - I submitted and was credited for a DL flight from NRT to SIN that I was on because my inbound AA flight was delayed and I missed my JAL connection. I simply submitted the boarding pass and 24hrs later got credited.