Brian,
I was with Defence, living in Canberra (with family) then posted to Sydney. I went unaccompanied, which meant Defence paid for my Sydney apartment etc for the 2 year posting in Sydney before I was posted back to Canberra. I kept the car registered in ACT, and my ACT licence. I was entitled to 4 "free" (paid for by Defence) trips home a year.
I went home normally every 6 weeks or so (busy job in Sydney with lots of travel, plus family enjoyed their Sydney Weekend "house").
My argument was (would have been) that I was maintaining a residence in Canberra, and regularly living there - even if it was only for the weekend. Luckily never had to test the problem.
I was reasonably comfortable with that scenario - but given your question it might not suit everyone.
I'm now with the AFP based in Canberra (but un-sworn - so not a cop) and my boss is an AFP Officer (Superintendent) and also an ex-VicPOL officer - he lives in Canberra but maintains his car rego in Vic (and also regularly goes home to Melbourne - but his family are here in ACT with him). Has done so for 15 months now.
Hope that helps......
