Everytime the 320 makes an autoland with AP 1+2 it is in fact carrying out the autoland with AP1, which is "master". AP2 is only there to take over in case AP1 gets u/s (fail operational). With one AP only, autoland is carried out exactly in the same manner, only you don't have any backup so that if AP gets u/s then the airplane cannot autoland, obviously. But in the bus they guarantee that the airplane will not be out of trim after the only AP tripping (fail pasive).
I don't know if concorde had this fail pasive feature. What a shame that it was decomissioned. It didn't even left any supersonic offspring...