UP&L operations can be found from 153.485 MHz to 153.71 MHz, in 15 KHz steps, and on 451.15 MHz. Main dispatch, Salt Lake City: 153.62 MHz.
Questar Gas uses Questar Infocom's trunked systems.
453.675 MHz 162.2pl Granger-Hunter Imp. Dist. (WVC)
From what I have seen, Nextel appears to be their primary system for communications. The 800 MHz LTR trunked system TCI used in the past is no longer on the air. The two UHF conventional repeaters I have heard them use in the past are still in service, though I don't know if they are still used:
461.95 MHz 123.0pl 463.775 MHz 123.0pl