Insurance companies generally resolve such matters between themselves, but in any event, notwithstanding the normal policy exclusion you quote, the insurer for a competitor vehicle involved in an accident immediately before/ immediately after and during a transit on an event would likely pay-up.
Even if it won't, SCCA's insurance costs are slightly less costly with the possibility of successfully challenging the applicability of the exclusion--the more the cheaper--than simply having no minimum mandatories.
Even if it won't, SCCA's insurance costs are slightly less costly with the possibility of successfully challenging the applicability of the exclusion--the more the cheaper--than simply having no minimum mandatories.