I asked Dr Robert Mesibov to help ID this one. His reply was: "The big Kosciuszko millipede is family Paradoxosomatidae, subfamily Australisomatinae, tribe Australiosomatini. The image doesn't allow me to ID it any further, and of course for a species-level ID I need an adult male! Interestingly, most of the Paradoxosomatidae in the high country (Kosciuszko into Vic) are fairly big animals."