I've been able to upgrade an AS50 award as an MVP. I just called at the 48 hour window and asked. I know that reps are not supposed to do this but I thought it couldn't hurt to ask. It sure made for a nicer trip to Mexico.

I would bet that this wouldn't work for full award travel. I assume the rep looks at the milage plan number to verify status. On an AS50 award, it will be the MVP's number (because AS50 awards earn miles).