'J' refers to the editor, Jeff Fisher.
This is an updated version of the Australia map that comes with Second Century (post WWII Australia needing an electric rail system). Industry supply chains have been repaired. The economies of various regions have been thoroughly reworked. Events have been added so you can affect fuel and track prices by hauling (or failing to haul) certain materials (e.g. reduce electric rates by removing waste to prove you supplied electric/nuke plants).
No, the rails in the screenshot are not in the starting map. That's just a pic from a finished game.