I would suspect that they do the same thing we do on the other side of the country and use local ham repeaters for the operations, with a ham group providing radio comms. Short range marshals' comms are done on FRS.
You could find out what car club is sponsoring the event and check TAFL to see if they have any radio frequencies licensed to them. Actually, I just checked the website, and find that the Town of Bancroft appears to be the official lead sponsor. So you might find some stuff in the TAFL or in the database here in Hastings County in Ontario - maybe the town might use some of their regular radios.