According to the web site, the NR is essentially back county after December 1, when services, both concessionaire and NPS, are terminated. People can use the campground (no running water) and technically you need a back country permit. The roads are not plowed and the entrance station is not staffed. My understanding is that the road fro Jacobs Lake is not plowed at some point, which should be a clue to vehicle users.

I have not ski toured on the NR, but it would be sublime with the usual good snow cover. It really is beautiful country, with access to whole vast vistas of the Canyon which are essentially inaccessible to the South Rim hordes. My visits have been during the time when facilities were open.