Guide for completing on 4 player co-op (boosting sessions), 1 person MUST collect all 3 fuses! Otherwise you cannot turn the power on. If you haven't/can't watch the video link, I've written a guide below which could be printed to have handy;
Open 'junction' door for 500
Open 'canal district' door for 1000
Enter beast mode, run under 2 bridges on the path, grapple up, run around to the electric box, open up doors with electric.
Run up the now open stairs (also says canal district above them), and run over the bridge, open door for 1250Find fuse 1
Open 'waterfront district' for 1000
Enter beast mode and immediately right, electric zap the box and open the gate.
Climb stairs, pass through to second room, open door for 1250
Cross bridge, over 2 small stair setsFind fuse 2
Open 'footlight district' for 1000
Enter beast mode, immediately right, zap open gates with electric.
Go up these stairs, open door for 1250Find fuse 3
1 PERSON MUST BE CARRYING ALL 3 FUSES
Return to the 'canal district'
Enter beast mode, run into the canal, melee open the big door.
Open the rift (move to another location)
Kill the gatekeepers.
Run to the far end of the room and place the fuses (obviously the person who was carrying them)(You can also enter beast mode here, zap the power up and enable Widow's Wine grenades, which helps to also get The Spider and the Fly achievement - please do not spend 4000 of your points on this until you have done the main achievement, when you have, you can all go back and buy Widow's Wine grenades)
Calling the civil protectors (try doing one each - so all unlock the achievement - if this doesn't work, just play again, with one person calling all 4 (play through 4 times for everyone). If you do this, the person calling all 4, will try avoid spending their points on opening gates.
Civil protector 1 - In the junction, from the spawn area, and slightly to the right.
Civil protector 2 - Canal district, right at the end.
Civil protector 3 - Waterfront district, at the bottom of the stairs, to the left.
Civil protector 4 - Footlight district, at the end, by the stairs
These cost 2000
to call each one.
Here is a video for visual reference;