I still have some listening to do, but so far I wasnt able to hear any of my calls. We were in the air, and off and on with SL approach on 118.15 between 10am and 12:15 pm (17:00z - 19:15z) on the 14th. There were multiple other aircraft shooting approaches into KPVU that were on with SL app on 118.15 with us during that time as well, and I didnt hear them either.
I'm guessing the frequency is not getting picked up or getting stomped on due to the other frequencies like mentioned above. Its very likely that 118.15 is on top of the mountain by the FFU VOR like mentioned above - SLC has radar down at KPVU so they can see Utah County traffic, so it would make sense for 118.15 be for Utah county as well, and I bet the reception on the ground in SL valley is terrible.
I may have to get a scanner and see if I can receive them from my place and start my own feed