It appears they are on the Palmetto 800 system, a Motorola II mixed system, both digital and analog. The database information indicates they are currently analog. Here is the link. You have to scroll down to find their talk groups.
Gold Cross in Richmond County is using MotoTrbo on their 154.2125mhz frequency so monitoring won't be possible with a scanner. Richmond County stopped funding for their use on the Palmetto 800 system over a year ago. Their road supervisors have 800 mhz radios to talk to first responders on scene. The Columbia County/AirMed channel is still analog.