That would make sense, SLCo doesn't have any 'single track' that are only accessible by motorbikes, everything is OHV or hiking only. I suppose they could motorbike into some of the ex-dirtbike routes but the controversy is mitigated by just hiking. Utah Co on the other hand obviously has a rocking inventory of single track that would best be searched by motorbike.
SLCo's are here:
http://www.slsheriff.org/searchRescue/joinTeam
From what I gather you have to make it to 65% of call outs, training & meetings in your first year. There are ~100 per year and can last anywhere from 1 hour (plus drive time) to full day. I know Seth Bowers was involved in SLCo SAR some years ago, there might be some other RME'ers that could chime in with some actual info too.
Found Utah Co's here:
http://ucssar.org/search-and-rescue/join/