I don't know if this is suppose to be legit, but I had a hack level 3 and I was able to hack a turret from behind a wall.
You can also hack the turrets on steel peel on the right side of the enemy spawn through the wall. This really needs to be fixed.
Yeah this is a problem. And I've seen enough comments about it, and people talking in game about it - that I'm sure the Dev's are aware of it. I expect it to be patched soon.
This, also the ability to heal a turret from behind glass, is possible. I mean, don't get me wrong, I do it all the time, but I know you shouldn't be able to.