I made a short, two-minute video demonstrating this easter egg. I KNOW you haven't seen this one before!
Your mind will be BLOWN FOR SURE!
The electrical boxes are supposed to show the electric shock symbol, but on top of the FIB Building, the electric shock symbol changes into a blurry "all-seeying eye" illuminati symbol when you approach them.
I've looked at similar electrical boxes on top of other buildings, and they don't change into fuzzy illuminati symbols.
This phenomenon occurs on top of the game's FIB building. The FIB stands for Federal Investigation Bureau.