The event insurance DOES NOT cover vehicle damage to any participant in the event. (that means anyone who is there for the event and signed the waiver) It may cover damage to a site-owner's vehicle, such as if someone drove through the fence and hit one of the cop cars at SPC.

Your personal vehicle insurance may or may not cover autocross damage. Some insurance companies do, some don't. Most will try not to, but if the exclusions on your policy aren't written just so... they might have to. (that's not to say that they won't then immediately cancel you)