Ok, I’ve finally managed to get a copy of the Hudjashov et al paper that I mentioned a few days ago and it’s far better than I thought (note to self: ignore pop. sci. overviews of things).
The major finding in this paper is that they confirm that Australia and Papua New Guinea were settled from the same emigrant group from Africa, dating back around 50,000 years. The spread of these people from South-west Asia to Australia took around 5,200 years. They also suggest that there appears to be signal for a second migration around 30,500 years ago from New Guinea into North Australia.
I don’t quite believe those dates – it’s just an extrapolation from a simple mutation rate (AKA rho), and there are better methods out there.
However, it’s definitely worth a look