It really looks like they converted the downstairs to a separate unit and this is the service tap. There is a meter at the bottom of that raceway that starts around 3 rungs down from the top (you can see the svc head). If you look behind the 6th rung up from the bottom you see the metering equipment.
The neutral loops in from the bottom.
You really need to blow the picture up to see all of this.
That still doesn't answer the question of what the guy was doing up there.
