Yes, the notch in the plate (receiver cover) is for passing the wires from the mechbox through to the receiver stub.
Some receiver stubs are filed flat on the bottom to provide room for wires. Some are routed with a groove/channel.
Some stock tubes have a channel cut on the inside for wiring...so the wires would fit (it's usually pretty tight) between the outside of the receiver stub and the inside of the stock pipe. That's the nicest setup.
Otherwise, you can cut into the stock pipe and run the wires inside the receiver stub....or route a channel in the receiver stubb and cut it short. Obviously these two options are more work.
In this day and age...where's the wireless AEG?!?
Best of luck,