A while back me and odst glitcher found a way to get out of Mombasa streets and onto the buildings near the uplift reserve flashback, ABOVE the barrier on foot. Its possible, but hard. Near the CM:UR flashback object there is a blue shield door. You can elevator over it with 2 people.
Once you elevator up, you end up on top of the shield door. Have the guy who is still back on the ground kill himself. He will spawn up in the air floating almost jesuslike, right above the barrier. Now the person who is floating must float over to this ledge thing with shafts. Then have th e guy on top of the shield door kill himselve. He should spawn right on the ledge with the shafts. By now your above the barrier, but theres no way to get up. Slowly make your way to the end of the ledge. There should be another super small ledge thats amazingly hard to get onto. You both have to slowly get on, move to the corner of it, and double jump up and onto the roofs. Now you are free to roam Mombasas roofs withought barriers! I will provide pics soon.