"No, their platform doesn’t support any real secure protocols and won’t route over a VPN, it needs to be on the same subnet as the devices. [...]"
They won't know that much. They don't understand that their job isn't running a water department, it's running the computers that maintain the water department and that includes security. For someone familiar with computer security it's easy to recognize negligence, but until the law sees it as criminal negligence nothing's going to change.
Small town municipal water departments aren't going to be able to afford the guy holding the shield against international state actors.