You need to be careful about what BA flights give mileage credit. While there is a blanket statement that you will not receive credit for transatlantic flights, I recall reading in the last issue of the AA timetable, that BA routes introduced after a certain date in 1995 are subject to approval. I check with both BA and AA before I book the flight.

Did you know that you can sometimes get credit on AA for BA code share flights? (Even though you may be told by AA that you cannot). I took a BA code share SYD-SIN last July, did'nt get the flight posted automatically so I sent in a copy of the ticket receipt and boarding pass - finally hit my account in December. Turns out it is up to BA whether they will give you the credit or not. Always worth a try.