score:2
I can't find all the timetables for the shuttle bus in winter. But I found this page for the shuttle between Nendaz and Siviez. There is buses almost every 30 minutes, except for a pause at the time of lunch.
On this other page (with lot of errors), other shuttle buses are described as running every 15 or 20 minutes.
My experience is that those kind of buses does not really follow a strict timetable, like other public transportations in Switzerland. They are only running just before the opening of the ski domain and just after they closed (9:00 - 16:30). Depending on the people they have to transport, they won't stop at the end of the loop and wait for the next slot, but will directly go and take the next persons.
Actually I'm wondering, why do you want to know the timetables? I think the routes are more important if you want to choose a hotel or rent a room where you don't have to walk too much.