I am having the same problem. Three of us due to fly on AA award tickets from LHR to MIA on British Airways next summer, but a schedule change made our connecting flight tricky, so I requested a change to a later flight, which is on AA. I have phoned in several times to check on the status. I have been told by each agent I have spoken to that my reservations are "locked in" and that no more miles would be required, but that AA has to wait for BA to release us from their seats in order to re-ticket.
When I made the change at the end of December, the agent told me it could take up to 72 hours to ticket. Each agent has told me since that it will likely take 30 days.
I remember when an impossible/unpalatable schedule change was like a Golden Ticket from Willie Wonka: I could request a much better itinerary, and generally, I was granted it. Times change!