Let me untangle this for you. The can on the left is 7200V to 240V... the can on the right is 2700V to 240V, and the regulator runs off 2700V.
They step 7200V down to 240, run it through a photocell, contactor and fuse setup; then into the secondary to produce 2700V to run the Regulator. It works great, they eliminate the need for oil switches... it's a win-win :)