How about checking the fare rules for the ticket?

Log on to united.com, put in the dates and route your friend is flying, and select the flights he/she is on. Click on the fare rules tab (if your friend's fare isn't available). In the address line, delete the fare basis and replace it with VXWEB1. The fare rules should pop up. If it isn't upgradeable, then it would be stated in the rules.

I don't know how else to find out other than calling up Res (which you already did). Perhaps others can be of help.