Blair, the lodge is some 30-35m above the valley floor so the height is noticeable. I can understand the the -18 at Perisher with that height difference and position at the foot of the slope. However Charlotte Pass is almost the same elevation, about 1750 in the valley where the WS is, to go another 5deg less than Perisher is asking a lot. That is why I think the WS must have been sunk 1m in that snow pack thus measuring only 50cm above ground. Interesting about the mean min relative to extreme min, good reasoning I agree.
SB I agree with Blair on the pine trees, they do live in much colder conditions, certainly would be zero effect from the tar or buildings. I agree the main problem for vegetation are the cold summer temps not the winter ones. Having no reliable summer warm period severely limits plant/tree germination.

Road too wide to be a back road so it's most likely the highway and I suspect like Blizz the around the top of the River Lett Hill or even a tad towards the Hassans Walls section of road (near the picnic area/lookout of today) is the most likely area and on the old road. That's my strong impression of the view.