That is a crazy amount of savings man, but not a good thing if you are trying to make a claim, is it?
CTP is covered nation wide, and my insurer covers me if I'm interstate. I have a QLD licence so it's easy to say I work in Sydney and had car down here for a few days.
My brother did the same thing for about 7yrs, and still got covered by insurance on some major panel repairs. edit: He got my sister who was QLD based to be a registered operator so he could maintain QLD rego.
I'm not advocating it, but it's quite a contrast in price between QLD and NSW, as I outlined in the CTP thread. The expensive NSW CTP insurance doesn't benefit the driver, it just means knobs who play in traffic will get bigger payouts. And it's also more expensive because the insurers collude to set the price and then RMS okays it, where as in QLD the Transport Dept set the price and Insurers have to come in under that.
edit: I have also seen a marked increase in QLD and SA number plates in my area.