It's possible this so-called 'staff pass' is really just a regular lounge pass the staff member earned as a reward for positive customer feedback? If it's got their name on it to be used by them only obviously you wouldn't do it as lounges overseas almost always ask for your boarding pass in order to charge the appropriate airline for your visit.
If it's just a generic lounge pass not assigned to an individual then this is no different to anybody giving a lounge pass to someone else to use.
I'd read the t&c's carefully as it may state it's only for domestic Australian lounges. If not, it may be able to be used overseas however chances are you'll probably only be able to use it at a QF operated lounge eg SIN, HKG, LHR not LAX for example which is a One World Lounge not a QF Lounge.