Cumulatively, the raises over the length of the current contract are the same as the tentative contract, and UPS's per employee contribution to heath care will be significantly more than the past contract, so PTers are in fact earning more.
PTers still in progression will get either the general wage increases or the new progression rates. For example, if the new progression stipulates that employees with one-year seniority earn $11.00 (up from $10), current employees will be bumped up to that rate when they reach one year.
There's still a chance a "catch up" raise is in the TA, but I would assume that information would have been leaked along with the general wage increases.
When I added up the contractual raises for '08-'13 ($4) vs. '13-'18 ($3.90), I wasn't terribly upset as it seems that $0.10 is going towards raising new hire pay. I'm more than willing to trade a dime over five years so someone coming in off the street can make more than they could flipping burgers. This will also (probably) slide the PT'ers in progression up a notch, depending on how far along they are. However, for part-timers out of progression (4 years of service or more) that are waiting to go full-time without ever having had the chance (the PT'ers in the 4-15 year range) there really should be a catch-up raise. But we won't know for sure until we see the TA.