Note that I said in, not on. (Maybe they do fit on an S, but I haven't tried.)
Picked up the 19-inch Cyclone Wheel/Winter Tire Package today from Tesla Burlingame. They're for an X, but I picked them up in an S. The staff were extremely helpful in getting the tires packed in, as well as very careful not to scuff anything along the way. This was apparently the first time they'd loaded a set of tires into an S, so they weren't totally sure it'd all fit, but it did.