From my experience, having been on a hot air balloon crew for a decade+ in the 90's & early 2000's:
MURS, even though FCC regulations prohibit their use onboard an aircraft, they are still used, especially 154.570 and 154.600.
VHF-High low power & itinerant channels, such as 151.625. Licensed or otherwise.
FRS/GMRS. With the recent rule changes, license by rule FRS useage includes all 22 channels with no more than 2 watts on channels 1-7 & 15-22, and no more than 500 milliwatts ERP on channels 8-14. If properly licensed for GMRS, higher power can be used of course. (5 watts ERP on channels 1-7, and 50 watts on channels 15-22.) As stated above and below, however, licensing isn't always done.
UHF low power and itinerant channels such as 454.500, 457.875, etc. Licensed or otherwise.
123.300 & 123.500 can be licensed for air-ground use between the pilot and the chase crew.
The crew I was on used CB radios. I've also seen non-commercial pilots and their crew who were all licensed Hams using 2m on up.
It is possible that commercial balloon companies local to that area could be using commercial repeaters or trunked systems, whether analog, DMR, NXDN or P25.