Dutch insurance companies don't insure on track.
However as Chip said the ring is a public tol road, however there is an exclusion which says: when you compete in any kind of racing your claim will be expelled.
Pretty hard though to prove someone was 'racing'. Downside is they would HAVE to pay but could place you on a blacklist which will eventually mean pretty much every insurance company won't get you insured...
Getting towed of the ring will be payd by the ANWB (a-a) though