Thanks for that research. It coulda been a stolen vehicle of some sort (for those that didn't already know it Lo/Jack can be installed in just about any good-sized transportable object that's at risk of being stolen -- bulldozer, boat, big diesel generator, etc.) on I-15, but I have good ears now, so it could have been the base transmitter at Mt Potosi or Black Mountain in Nevada, too.
Who will be the first radio-geek here to get Lo/Jack to install a receiver/RDF setup in their home or car??
I imagine there have got to be some sophisticated car-thieves & chop-shops out there who know to monitor the Lo/Jack freq with lots of receive attenuation when driving or chopping a G-ride, & maybe immerse the car or chop-shop in a localized jamming signal on the Lo/Jack freq so the transponder doesn't hear an activation signal. That's why Hooligan's Hooptie may or may not have Onstar, instead of LJ, though Onstar still has vulnerabilities too.
Back I think 20 years ago now I got a nice demonstration of a system called Teletrac. It used 900MHz spread-spectrum. It was a cross-between Lo/Jack & OnStar -- once activated, your vehicle could be tracked (by TDOA, not GPS), deactivated, etc. but the cool thing was it could also monitor audio inside the car.
ANYWAY, for you scanner-dudes up there in the Wasatch Front, remember not to get all excited & call 9-1-1 whenever you hear a data-burst on 173.075, because it is most likely going to be one of the base stations trying to activate a receiver or set it to ping itself more frequently once the hunt is on. Also, numerous times (I used to live 250' above the ground in Detroit...) I've heard some locals get all excited about a Lo/Jack signal, spend time trying to locate it, & then finally discovering that it's a known-recovered stolen vehicle being owed by a tow truck or sitting in the impound lot, with the network not having sent out the deactivation signal for some reason.