E-ticketing works only if you have all your dates down pact and will not be changing dates that much. It may not necessarily work on open-dated segments either. The problems come in when you've got an e-ticket on AA stock, and you have an open segment between say HKG-LHR currently booked on BA. At the airport, you realise that the flight is full and you'd rather take CX. You cannot simply mosey on to CX and say you want to get on their flight. You have to call AA, who will then reissue the ticket as you are basically changing airlines. Whether or not they will charge you the reissue fee is unknown at this time.

Also, with date changes, in my previous experience, AA's stupid system sticks in a "valid on date shown" even on full fare ticktets that permit date/airline change. I, again, don't know if they will charge you a reissue fee because once you change dates on an e-ticket, or for that matter, once you change flights even on the same day, AA has to reissue the entire ticket!

Basicallt it will involve a lot of long distance calls to AA res agents. If they're in the US, that's fine. The problem is when you attempt to call an AA office locally and they don't know what's going on. Reissuing a simple segment may take at least an hour or two. What if you're somewhere where you don't have an AA rep? Would CX be able to take over the AA res and assist with reissues?