There is no dedicated Winter Camping Section (group of people) that I am aware of.
There is a Backpacking Section, but they operate mostly in the summer.
There is a Ski Touring Section, and they do some snow camping, some hut tours, and some cabin trips.
There is a Peak Climbing Section, and they do mostly non-technical peaks, but not much snow camping.
Then about once per two years, there is a Snow Camping Seminar, and it typically has the two evening classes plus at least one field trip. Several years ago, there were three experienced leaders set up for this series. Suddenly about five days before the field trip, two of the three popped up with work conflicts. The third leader could not bear the thought of 18-20 beginners on her hands, so she called me, since I had led beginner trips for yet another activity section. So, I went, and then the work conflicts dissolved, and we ended up with four leaders for 18-20 beginners up near Carson Pass.