That's a little strange to me as for my AA bookings aa.com "my reservations" tool tend to show the whole ITN for reservations with all the "Amadeus segments" (=BA, LA etc.) as well. The information is not updated in real time for non-Sabre airlines, though. So if I have a booking made by AA and I select/change a seat at ba.com for my BA flight, that information is not visible at aa.com at all, only the original seat reserved by AA themselves at the time of booking is showed on aa.com.

Another thing I find a bit strange with one of my AA bookings is that I cannot see the CX segments with any Amedeus based system (Both BA MMB and checkmytrip.com are showing only those CX segments which are immediately connected to another flight). If someone has an insight how to view the AA booked CX segments in real time, I'd be more than happy to know. I do have the CX locator but as I have no Asiamiles account it doen't do much good.