Aircraft like these can be operated in the Restricted Category whereby mods and airworthiness requirements are modified or not required for special purpose flying. Australia like the USA and Canada has a Restricted Cat.
All it takes is some Gumnit half-wit to sign off. One reason they don't like ex-mil aircraft hanging around is their perception of latent liability. In other words the lawyers are running the show. Uncle Sam's mob has no such issues. I'll leave this to the Canberra "flat earth society"...
