Per Missy's suggestion, I just called the Gold desk. I was told "whenever we request upgrades for tickets on American or any other carrier's ticket stock, we send a cancellation of the ticket to the other airline when we modify the record. So the only way you can get an upgrade when on another airline's ticket stock is to make your request on the day of departure".
I am not saying I buy this explanation (even though she did go away and ask someone else). I am simply reporting what I was told. This continues to be a can of worms IMO.
I am going to cancel my current res that is on hold.
this explaination is the one i had received two years ago - and i think it is accurate.
some of you may remember the past - when we were upgraded on codeshares. then all of a sudden it was becoming a problem and it couldnt work anymore.
in retrospect, it makes sense, because there were always problems at check-in if i was upgraded on an AS portion of an AA codeshare
when the first flight was operated by AA (and you checked-in with AA). the agents always said it appeared my reservation was cancelled, and had to make several calls to get my boarding passes issued. it was never a problem when i checked in with AS - mainly because the AS computer had the correct information.
another way to look at it - in this day and age of etickets - everything has to match exactly. in the past, flight number changes (either through schedule change or voluntary) didnt matter because a boarding pass could be printed with the correct information and attached to the ticket. as airlines moved to etickets, the information must match exactly. (every time there is a schedule change that involves a new flight number, etickets are reissued). when you are upgraded on AS, you are moved to the U bucket. the AA computer looks at a reservation that is in U class and sees the ticket is in L class - those two dont match up and thus the AA computer rejects the reservation. at least that is my take on it all.
i dont think AS is trying to screw anyone over - i think there are compuer system limitations and it stands that you are upgraded in advance when you are on AS ticket stock only!