Most SCADA systems are on closed networks too and will use rather proprietary systems. I can swact radios and stuff on ours at work, I could bring down the whole north if I needed to, and when we used to handle cell sites I could turn them down and up as needed. But an average person who got to a computer and was lucky enough that the app was already open would still not know what to do.
Though I suppose someone with experience would at least know where to look, if they broke into a building that had such systems. A tech might have his laptop open with a sticky note with a password etc and you go from there, then dig in documentation. Depends how much time the attacker really has.