I was able to confirm upgrades for 3 persons (1 ITIN, 2 x Elite members = 3 SSWU) on YVR-HKG in July 2010. Mind you, it was the 2AM departure but it worked for my family.
I phoned at the 4 day window, it was immediately confirmed, and it was an expensive Tango Plus fare (being summer). Unknown what was the space availability was on this day.
Good luck!