there aren't that many open practices... but that's the real reason I went out for the all event tickets... hope you find someone willing to give those babies up!
The 20-minute warm-ups (with no skater's music played), typically held a few hours before the competition, have been considered practices in the past, except for a few occasions when local folks briefly claimed they were not practices (despite being listed on the practice schedule) and did not permit those with practice passes to enter. I think ticket holders for the following competitive event (probably would be an event different from the event being warmed up) *might* be able to get in to see the warm-up if there is only a zamboni break in between, because they admit ticket holders quite a bit before the event starts. No guarantees on this, though, since arena policies and practices very. Remember, too, that many of the warm-ups will be held at Pleasant Arena and will therefore not be open to practice-pass holders.
If you are referring to the 5- or 6-minute warm-up before each group of 3 to 6 skaters competes, that's definitely part of the competition and does not require a practice pass.