I think some of HAM frequencies may be used as satellite "bouncers".
but that requires Ham license which SAR team has?
Most of us have our HAM license.
We use repeaters (ham stations in good locations that simply repeat the message), the moon, and space station(s).... but it all depends on what frequency you're licensed to use whether or not the moon, atmosphere or space stations are effective repeaters.
Mobile cell towers? So its basically a portable cell tower? How does that work? I might look into getting one of those! Lol but ill post back up how well this works
it's a trailer with a big, metal stick on it

funny, though, the problem with those are people use them and overload them.... ever heard someone say "I've never got reception here" - it could be they're 'using' a portable repeater... which gets overloaded.... which makes the purpose for hauling them to the site (SAR/1st responder/police use) pointless.... our job isn't public service
I asked the HAM guys in our SAR group - to say they were skeptical would be an understatement.... so do update your experience (their point was, that's great that you get your signal out; but the transmitter for the cell tower doesn't boost its signal to get to you - so it wouldn't work....