The electrical system can be used to drive elevators and turn lights on and off. The additional buttons at the top and bottom of the elevator shaft are used to call the elevator to that floor.

Everything that operates off a button is physically connected with wire tiles and visible in game. There is no secret logic. Although I suppose you could obscure it a tile layer - I actually have an idea for an x-ray level gimmick based around that technique.

The color fading system normally used for level transitions is re-purposed here for a subtle lighting effect.