The Rockville SC told me they will not mount any tire (including the OEM tires Tesla sells) on a third party wheel. Nor will they mount a non-OEM tire on the Tesla wheels.
I have the 21 inch wheels and am replacing them with the 19 inch Tsportline wheel (21 inch low profile Michelin Pilots are too prone to bubbles from all the potholes in my area). I was willing to buy the Primacy tire from Tesla, but they refused to install them on the Tsportline wheels. So, I am going to, of all places, Costco to have Michelin Pilot A/S 3 tires installed on the Tsportline wheels (none of the installers Tirerack had referred me to for installing tires purchased from them would work on the Tesla, so I have no choice; Costco's price is the same as Tirerack and includes a 5 year road hazard plan).
Tesla SC said they WILL balance tires, rotate tires and align the car once the wheels/tires are installed on the car. Makes no sense to me, but that is their policy.
BTW, I'll be selling the gray 21 inch wheels afterwards, if anyone is interested.