I'm not a pipeline expert, but I've been doing computers sense the early 90s. You have a pipe. It has pumps and valves. You have a computer that controls it all. The computer gets hacked. UNPLUG THE DAM COMPUTER... and plug in another one. Then restart the pumps. If they are too incompetent to figure out a workaround then get the hell out of the way and let someone else try.
If there is one thing I've learned with computers its that the guy at the console is god. There is no such thing as taking over from a remote location. Anyone that tells you differently has been watching too many movies. Send real actual human beings out the the pumps, unplug the dam computer and just turn the pump on manually. Yeah, a person might have to watch the pressure and flow rates etc rather than the computer. So the hell what. Get the dam gas flowing again morons.
I can understand why you think they can just restart it all without the computer. It's really not that simple. There are instruments for density, leak detection, flow rates etc. all along the line. These instruments are needed to turn pumps on/off as well as valve control. All these things work in unison for safe operation.
To use different computers would take weeks to rebuild the control systems. Also you would have to be sure that the virus has been cleared from the field instruments or it could re-infect the new control systems.
This is what happens when your network security is lacking. I know this because that's what I do IRL.