Bent,
There is no difference between adding A320's onto an existing AOC and setting up a new AOC.
Both require the same amount of work as the AOC review and issue process needs to be completed in both cases.
I can assure you that the Alliance infrastructure is such that adding a fleet of A320's would be difficult - not impossible - but difficult and would take in the order of 6-12 months from pushing the button.
Having said that there is nothing to say that the button wasn't pushed 6-12 months ago - but I see no evidence of that thus far.