AVDATA is merely the collection agency for the airport operator - the real issue is the basis on which the operator is entitled to recover landing fees etc from the registered owner of the aircraft. This would depend on the circumstances that exist at the time - was the operator's consent/permission required, what notice of charges was given, etc? Whether the airport operator can succeed in litigation will depend on how well it can prove its case. If the only evidence before a court were AVDATA's recording and an aircraft owner's evidence that the aircraft was somwhere else at the time (eg another state, in maitenance) it is pretty easy to guess which way a court will lean. It is all about having a good case and a good lawyer. If AVDATA is wrong and continues to bluff, call the bluff.
On the other side of the argument, I know of one local MBZ where the place is alive at midnight but few calls are broadcast.-A similar situation occurs early in the morning at a local CTAF, the main perpetrators being bank runners. Bloody annoying (particularily given the arrogant attitude of some of the pilots) and potentially dangerous, and an unlawful use of the airport/aerodrome owner's property. Owners of airports are right to want to recover the charges they are entitled to recover, and the AVDATA system may not provide the proof that is needed.