Wow, allot of debate on this! I figure I will give a little more info on the system.
Scott, this is not LON works cable. There is a LON works comm link from each genset for generator control but this serves a different function.
Here is the PLC. There is one in each generator. They all have this network card. The other end of the cables come together in a master control cabinet where they terminate in an 8 port router which I don't have info on. The router is connected to a DSL connection and has an Ethernet cable running elsewhere inside the control cabinet. I'll post a picture tomorrow.

I think Solarpowered hit the nail on the head.
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I'm thinking this is a case of the guy thinking, "Shielded is better than unshielded, so I'll specify shielded."
The engineer will never admit he speced something wrong.