My experience is different for EWR and everywhere else:

In EWR if you ask at the counter they will tell you that it has to be done at the gate. When you ask at the gate they will tell you that there is no chance of the upgrade and they will not add your companion to the list. Twice I have been told that there is no chance of the upgrade and got battlefields for my companion after I got them on the list at the President's Club.

In every other city that I have been in this year the agent has happily added my companion to the list at the check in counter (even if not a possibility) and on one flight from SAN we both got the UG when checking in 7 hours prior to departure.

Keba