It seems that they have removed the link from their webpage, but the details are as follows:

Club members can stand-by at the gate for upgrades within North America on their day of travel. They can continue to reserve upgrades 24hours in advance on all full fare tickets.

I'm not sure if the stand-by upgrades from any fare can be used on AA, but I would doubt it. As well, I don't know if you can upgrade a second person on the stand-by from any fare rule change.

Hope that helps!