The license conversion these days consist of a validation of one's State license followed by a PNG CIR exam followed by ATP Air law exam. (Have no idea re the CPL conversion)
Once done the PNG ATP license is issued.
Whilst PNG has attached itself to the NZ Air Law system (seems very similiar to that of the States really) I would not see that as any impediment to any other license holder from any other country.
Re pay ....guess every one could have their own deal but Aussies and Kiwi's seem to get paid in $AUD so those that live over the ditch do rather well in their home country due to the Aussie/Kiwi exchange rate
Regards who can get work in PNG as either pilots or Mechanics/Engineers, I have met, and heard, over the radio many different different accents.
PNG is a great place to fly, cant comment on engineering, but I must say that it can now be a somewhat hard place to live.
Vee tail...don't banish Kiwi's, otherwise the Aussies will have to find another group of citizens to bag.
(humor intended)