^This. If AA cancelled my original flight and replaced it with a BA flight but did not put me on it,all other things equal, which is what happened here, I would be on the BA and I would not be paying any surcharges. It's not the OP's problem they changed the schedule and/or operator and in this particular instance has made a very public reason as to why they did it. The easy answer is to just have AA refund the ticket, but a lot of times that isn't an option for people (reward space on alternate carriers is gone, prices have gone up, etc). Being asked to be put on their JV partner, which AA/BA/IB make such a public to-do about anyways, without any further costs or surcharges is a reasonable request in this instance.

Just over X-mas I had seven people travelling to Italy and one person was on a J award. These tickets were booked on February 10th of 2013 and at the time, AA's JFK-FCO nonstop was still scheduled to run in December. Sometime over the summer AA decided to end the nonstop in October and re-booked us on Iberia through MAD. The times on Iberia didn't work for us, but BA through LHR did. Suffice it to say, we were rebooked on BA LHR-FCO and I did not have to pay the surcharge for the one award ticket for the BA hop to FCO (although they did try). It's all about the delivery and handling of the agents on the phone.