I believe the part-timers that are sold out are the newborn ones rather than the employed ones. 1 year benes, still 8.50/9.50/hr, token raises.
I would have no problem giving away part of my raise to part-timers. Been there done that. Any part-timer should be making at least $11/hr after 1year and $14/hr after 3 years.
It will come down to putting the PT'ers into a position to take action. UPS and the union minimalize all give-backs and etc until it's too much to take. They would rather the PT be uninformed on each side. At that point (MAYBE 2013) PTers will actually be voting on the contract instead of letting it slide.
Also, with Hoffa around, negotiations will not be getting better for part-timers. I remember last contract the union and UPS were selling it at the front door to buildings but only to the part-timers. They weren't going to pull the wool over many FT'ers eyes.