Michael, I honestly don't know anything about this species. I guess it would be ok to confirm as the only other similar species I was able to find is C. sagittifera, which occurs around the Blue Mountains. There is another sighting of C. oligantha in the vicinity, so it is probably a fair assumption that this is the same species.
I have never seen this species either, but the location and the rather purplish colouration fit with what I would expect. The common name of this orchid is actually 'Mongarlowe Midge Orchid' and it is restricted to this area.