Costco are quite happy to fit tyres to wheels that are brought in not fitted to a car. They even have a box to tick on their form for wheels on their own, so I left the car on the vehicle lift at home, took the wheels to Costco in the other car and got the tyres fitted.
I haven't yet conclusively proved that the car can work out which tyre sensor are fitted, but someone from the OEM who knows what he's talking about said that the car works it each drive cycle.