I always thort that to operate in another country like PNG, one has to get permission from the country concerned...as we did. While CAsA may have some interest in an Oz registered a/c, once you are out of Oz ..what then.
On one trip to PNG many moons ago I got a lovely document from the " International Division" (sic..very sick) from a lady who shall remain nameless, PNG hadnt even been contacted and this doc stated Here is your permission to operate in PNG !!. It was all bumpf. Actually it was the PNG entry permit for the aircraft and the job that "allowed it", organised by myself.
All that "fake job" rubbish has since been changed, or modified as CAsA does continuously to keep you even more confused . Last trip, PNG clearance from CAA POM and off we went.
Nauru.. we just went there, by permission of Nauru Government./Lands Dept who wanted the place mapped. It must be about the only Republic that you can fit in a single shot from FL170 NIce place to visit for just 2 weeks, and the Surveyors opening remark was 'Welcome to the Alcatraz of the Pacific !' Which now it is.
Certain HF frequency was required tho, ditto for PNG. Isnt there a lot of water out there tho.?