Did anyone else spot the fact that - erm - there's only two rails in the picture? Or is there some part of the country where they use a beefed-up version of the Hornby system?
I suspect that it was policy to show only 2 rails, lest people thought that tracks without a conductor rail were safe. Electrocution is unlikely on a non electrified route, but the risk of being hit by a train remains.
I am not aware of any mainline railway that uses the running rails to supply traction current as is done on model railways.
IIRC▸ , the Volks narrow gauge electric railway DOES use the running rails to supply traction current, positive on one rail and negative on the other. At the remarkably low voltage of 50 volts. This requires special rolling stock with insulation between the wheels on opposite sides of the vehicles.