When you spawn at the top of Escalation turn to look at the doors of the old house, then on your left is a small L shaped wall.
Walk sideways to the inside then get up against the wall by tapping A, then lightly tap the left thumb stick to the right until your back is directly in line with the corner.
So then if you push up on the left thumb stick it should have the icon giving you the option to climb over. When you do it right you should realize that you are now standing on the wall go to the end of the smaller section and have a team mate stand against it
Note: tell them not to press A, just walk as close as they can then all you do is walk onto their head and jump into the fountain.
You should then be hidden inside the fountain.