(you will need force jump 3 and speed 3 before you attempt this)
from the sniper position jump up to the ledge on the left hand side follow the ledge round tell you are facing the wall in the dark, jump up and forward. you will find your self on a ledge turn around and look out to the ops wall to where you stand. the wall has a open bit to the base of it. what you are aiming for is hitting that wall just above the open bit. to do this you need to have full force and then put speed on and run forward and jump before you fall down. when you jump hold the button down. don't depress jump. the distance is quite far and to make to to the other side you need to strife in the air. when you hit the opposite wall you will wall climb up at this point (still holding jump down) face to a point up on the top of the buildings and you should make it.
That's my best attempt to describe how to do it via text.
Good luck and once you master the strife bit in the air to get the distance its easy.