I've been curious about this as well and have done some digging. After spending some time on ebay and mucking about with VIN numbers in an EPC I can't find any official rear handles. This is what the doors look like in the EPC, no rear ones, front only.
I've got that same print out. It does look as if there are only front handles.
Here are a couple pictures I have saved to my computer, of a 3500HD Crew Cab truck. I got the link to the Ebay listing by searching for the "rare rig" thread here. As you can see, the rear door handles look the exact same as the front ones, locks and all.
It would be cool if an electric switch/lock cylinder could be put in there (like the older Corvette). Not sure what to use if for though, maybe an alarm or to lock/unlock all the doors? but that would be better in the front door anyway.
Just thinking out loud.