I believe AA and TK still have an interline agreement for situations like this (AA also has interline agreements with other airlines like UA, DL, LH, LO, EK, etc.). It's nice that they did not make you take a connection through DOH or somewhere else.
Yes, they had the interline agreement but AA didn't rebook passengers to TK unless there is a last-minute IRROPS. That's why I was surprised that the OP was re-booked to a TK service and that's why I interpreted this as a gesture.