I think you are oversimplifying the situation. With any plant of sufficient size, there will be a lot of people involved in commissioning, servicing and operat

I think you are oversimplifying the situation. With any plant of sufficient size, there will be a lot of people involved in commissioning, servicing and operating it. This makes "fully insulating" SCADA systems much harder. Management people will demand to get data from the plant to manage utilization. Servicing personnel will want to connect their laptops to the automation systems to talk to their company's devices that are installed in the plant during maintenance. ... ... So, for military projects where integrity/secrecy is a value for itself, I can imagine draconian regulations to be in place soon, or most likely they already are. But for "normal" industrial plants where there's a need for money to be made, there always will be a balance between IT security and pragmatism in running the damn thing. And if diagnosing a failed motor controller in a stalled plant is delayed because IT security prohibits the technician from inserting his USB stick, I can tell you how the discussion with the plant manager will turn out in 99% of all cases.