Its an idea thats alway bouncing around, mixed in with attempts to make the delaware waterfront a tourist destination. It sounds like, besides a new PATCO route to Gloucester County, the plan is to link a Subway-Surface type trolley in at a reactivated franklin square station to the freight tracks on columbus blvd. Those tracks now stop near race, and are in the median. As you go south, i believe it becomes double tracked below washington. There are a number of spurs onto piers and into warehouses. I'm not sure at what point it is presently used by freight traffic, but odds are they could work out a deal similar to the Riverline.