Thanks to |TCB|TehBreakerPanel for finding most of this.

The fuse box is NOT required so you can do this without being the traitor.

1. Go to the middle of the map next to the spiral staircase. Next to some barrels in the corner, there's a ledge to the left of the bridge (with a metal beam). There's a dollar next to the beam.
2020 UPDATE: It seems the dollar bill can spawn in 7 locations at the start of every round. It will not always spawn! (There's a roughly 33% chance a dollar bill doesn't even spawn)

Locations are as follows:
Case 1 - on the base of the left pillar leading up to the central staircase from the showers. This is the location shown in the video.
Case 2 - on the left supporting beam above the ticket booth. When spawning in, go to the left side of the ticket booth and look up at the vertical beam going to the roof. The supporting beam with the dollar bill is connected to it on the right.
Case 3 - on the roof area (sniper's area). Walking up the slope from the traitor room on the side of the map, it is on the very left of the supporting beam in front of the blue barrel.
Case 4 - in the very top back left of the map (when looking at the map from spawn). It isn't in the changing room, but above it on a ledge.
Case 5 - on the ledge of a circular window in the new greenery section. This section is at the back of the map, enclosed in the staircase to twisting slide area.
Case 6 - in the generator room (with the vending machine that can bring you to the roof, right side of map. Not to be confused with the new generator room on the left of the map with the traitor tester charge!) on top of a set of shelves.
Case 7 - on top of the crates at the back right of the map, next to the traitor room entrance.

All locations can be seen here.[imgur.com] Photo 2 might be bugged and be at the bottom.

2. Take the dollar to the vending machine furthest to the right when you exit spawn (the vending machine will be facing spawn).
3. A white light will turn on - press the button.
4. Go to the showers - there will be a hole in the wall. Press the button.
5. Go to the spiral staircase and go up. There is a brick you need to press in facing the showers.
6. Press the middle button inside the ticket booth.
7. Press the valve on the roof area, above the hallway/machine room.
8. Go to the machine room and press the Yellow / Black square next to the door.
9. Type in the code '586371' and enjoy!

EDIT: Video Tutorial (PLEASE READ STEP 1 FIRST!)