Those two camp grounds are between Jindabyne and Thredbo so yes you would be able to get there during winter with chains. Nor sure if they are open or not to winter camping though.
I visited both places back in Easter. All you need is a permit to access the National Park as there are no camping fees. The next best alternate is Kosciuszko Mountain Retreat. I know it is open all year round, is cheap and the facilities are all you could ask for.
Am, planning to take my camper to the snow this year sometime.
Check them all out on my website at http://www.aussiecampovencook.com/kosci ... alpark.htm