The handhook expands on that;
"For different applications, such as different rate schedules, this requirement allows a second service for supplying a second meter on a different rate. Curtailable loads, interruptible loads, electric heating, and electric water heating are examples of loads that may be on a different rate."
I am not sure why that needs another service (they can simply split the metering after the drop) but since this is a utility decision it is really out of our hands.
Another place I could see 2 services is if the primary loads come in on a medium voltage drop with customer owned transformer and they want some 240 for their firepump.
I did see that once. I think the emergency panels ran off that too, with transfer equipment to the genny, but it was a while ago so I am not sure about that.
