The known TGs are listed here:
Fairfield County
If it's something big like the Lancaster Festival they may request an event channel from MARCS. Operations for events may be low key enough that they just work on the main or tac TG. If they have OSP or other non-county agency working with them they'd probably opt for an event TG. There is a communications plan in place countywide. When the Sheriff runs backup on Pickerington high priority runs they communicate together. I've heard several times on manhunts, chases and even a bomb threat at Meijer and they were using known TGs.