I think it's well to the right of the supercharger and distribution cabinets, if you're standing in the road looking at the chargers and Red Robin. They were digging a hole there when I took photos at the end of October - posted here or there's a link to the other thread I posted in.
Because of the large current (about 800 Amps per phase for an 8-Stall Supercharger Site) on the 480 Volt lines and the need for thick wires there, the transformer is usually pretty close to, but outside of, the Equipment Enclosure. Long trenches usually carry the medium, distribution Voltage (12-35 kV) lines from a pole or MV Vault to the transformer.
Someone needs to compose a Tesla Owners' Ballad, "Waiting for the Transformer"...