John,
It might be a safe bet that CASA has approved PAPI as an acceptable alternative to T-VASIS based on cost and pressure.
As a pilot who's been flying in and out of Gove for some 14 years, I can only reinforce all that ITCZ has said. And add, that whilst PAPI might be the international standard, I believe T-VASIS to be far superior (I think T-VASIS as an Australian invention pre dates the International Standard PAPI too!).