In my case, it's to provide IP connectivity where it is otherwise not available.

I'm using the devices shown in the bottom of the picture at http://www.digi.com/products/wireless-routers-gateways/routi...

These electrical substations are in the "middle of nowhere". We can't exactly call up the cable or telephone companies and get an Internet connection installed. Fortunately, cellular service is available, even though it is extremely slow in some of these locations.

The devices are, at their most basic, cellular routers -- a LAN port on one side connects to the industrial equipment equipment and the device connects to the cellular network to give them Internet access. An IPSec VPN from the device back to the utility's office provides a connection to their management software so that they can communicate with the industrial equipment.

The industrial gear is "smart". Need to disconnect a customer because they didn't pay their bill? Send out a digital message and their electricity gets shut off. Huge storm roll through the area? They can quickly see how many customers -- and where -- are without power.

IP connectivity to the industrial equipment means they can control everything from their main office and not have to do a "truck roll" for every service change and such, saving them tons of time and money.