Disagree. Why connect them to the internet? They should be super hardened against attacks, and should NOT have a physical connection to the internet. Same with electrical infrastructure. Network access? Possibly, however that network should NOT be accessible from the internet.
The only exception I can think of would be for meter reading, which should be a separate, read only device with no ability to do harm altogether.
People start freaking out at the costs of dedicated fibers to every monitored facility. Hence even 'private' networks still run over the same actual lines as the internet.
At a few of our sites, we have webcam-pointing-at-gauge. Deemed secure via air gap and simple to deploy.