Wirelessly posted (BlackBerry: BlackBerry8530/5.0.0.601 Profile/MIDP-2.1 Configuration/CLDC-1.1 VendorID/417)

Not sure what this has to do with BA, but 40 minutes is the MCT for AA domestic to AA international at JFK. (Since US and AB both use T8, I imagine that it's a legal connection for flights operated by those carriers.)

If you miss your AB flight, AA should re-book you on some other flights that evening if there is space available. You might be booked on another AA flight, but not necessarily via LHR; it's also possible that you would be re-routed on BA or even IB.