Yea, there are are number of areas you can get cams accreditation for...
From Scrutineers to paddock support marshals, to flag, to track, to tow, recovery, Drivers support, medial, fire, spectator control list goes on... Every person who works "track side" or in the moat at a Motorsport event, needs to be licensed under CAMS for insurance purposes..
And you are correct, CAMS licensing and regs state that any CAMS motorsport event, must have Fire, Flag and Medical onsite.. so without the volunteers, a Race would Literately not go ahead !