I once applied for a tech job @ Exmouth. The US had handed over ops to Aust ADF, whe handed it over to Contractors. The work was with VLF submarine comms, HF radio, and Sat.
I guarantee that no Aust personnel were privy to any comms content.
Back when US set up Pine Gap, everything came in on big unmarked grey jets, usually at night. As far as US is concerned, Australia is an untrusted foreign country.