Update:
You are able to shoot through the marked rock.
You are able to get on both Refinerys
GDI side:
Walk on the tank blocker collision
Jump on the collision at the Refinery
Have fun with beacons
Stuck a buggy at this collision
walk on the collision on the top
Have fun with glitch beacons
I think on Nod side, it isn't a big problem, because you need a buggy for that, but on GDI side it is very easy. Just set a blocking volume to the part, which is marked with 3 and you wont get any problems. On GDI side you can put a Blocking volume around the tank blocker.