My guess is the electric motor and batteries are in the fake engine. It's probably just a plastic shell. I don't see any wires coming out of the tank and you would want to keep the heavy parts as low as possible.
With 3d-printing, they could offer various 'motors' to match what ever motorcycle brand you wanted.
I don't see any wires anywhere. Perhaps this uses a crank sensor to apply the electric power. The faster you pedal, the more juice gets sent to the motor.
The "engine" reminds me of those cheesy radio/tape players that looked like minature 1940s or 1950s jukeboxes.
The front disc brake looks out of place on this style of 'bike' and is mismatched with the rear brake. Why not go with 2 discs or 2 drums?
Those E-trackers are beautiful bikes and ride awesome! My friend has one, I believe it starts as a Felt frame and is re-worked by hand. Crystalite motor, 3000 watt controller, feels very solid and well balanced to ride.