Despite the substance of the previous discussion in this thread and elsewhere, it remains unassailably true that there is no legal requirement, in Australia, for car drivers or owners have insurance cover for liability for damage done to a third party's property by the vehicle. I am not required, and I do not have, millions of dollars of third party property liability insurance to cover me to drive down and park in the main drag of any town or city.
I have never been asked, by the operator of any aerodrome, for evidence of insurance cover required by the operator's 'conditions of use'. In any event, evidence is easy to concoct and provide if required. That might be awfully naughty and perhaps even fraudulent, but it doesn't create the cover to respond to the liability of the uninsured naughty fraudster, if it arises.
The operators of the aerodromes the use of which include mandatory insurance cover like these are setting their own trap, for themselves.