To answer yor question, to a degree, the UP C40's in the 9000 series are for the most part ex C&NW units. I worked the Q157 from Kearny for a couple of months earlier this year, and I had the same question asnwered to me by the supervisor of the South Kearny engine relay service facility. The westbound trains they normally(althought not exclusively) go west on is Q157, departing Kearny at 2 AM, destined for the UP's Global intermaodfal facilites in the Chicago area.(They have three seperate ones so I'm not sure which terminal they do go to). However, to get to the facilities once in Chicago, the locomotives operate over trackage that requires cab signals, and these units are so equipped. it should be noted, also, that the UP/C&NW cab signal system is not compatible with the system used on the former Conrail system. The use of these units insures no power change is nedded to get the train to the terminal for unloading/reloading/reblocking, and continued further westward travels.
I know I'm getting old... My insurance company sent me only half a calendar this year!