Ski Resorts Summit County (UT)
From The RadioReference Wiki
Park City Resort Radio System Trunked in 2012
The Park City Ski Resort appears to have gone "trunked." When I visited last year (2010), the system operated the way it appears in the RadioReference page for Summit County Ski Areas - 5 UHF channels in the 450-460 MHz band using 162.2 tone.
In my 2012 visit, I started out monitoring what had been the Ski Patrol frequency, 462.9500. I heard a little activity, but nowhere near what I'd come to expect. I also couldn't hear anything while using 162.2 tone decode. I searched all the tones (both analog and digital) and couldn't identify any tone in use.
I listened to the other listed channels, and found one - 161.4750 (the "Grooming" channel) - that was very busy. It had lots of ski patrol traffic, but also lift maintenance, ski school, parking lot and more.
Then I noticed that some conversations that were clearly "in progress" were "interrupted" by totally unrelated conversations. Now, I was skiing while doing this monitoring, so I couldn't switch channels to see if I could find where the original conversation went. But all signs point to "Trunked."
It did seem that one physical repeater was being used first for all communication on the system, and the others were only used when a second simultaneous conversation was initiated.
One other thing I noticed was that each of the five repeaters was keyed up for about a second, about every ten seconds - sort of a beacon. Not sure why, but that made listening kind of annoying.
I was listening on a Kenwood TH-F6 ham radio, that does not have trunking capability, and I didn't bring a trunking scanner, so I could not investigate farther. Hopefully someone with more detailed information will edit the wiki!
2016 UPDATE The Trunking behavior I described above has been consistent for 5 years (2012-2016), and it matches the description of an LTR Trunking System. I'll be back next week and see if anything's changed.