The two tank cars are either headed to, or coming from, GEO Chemical in Harrison, the only customer on the Center St Branch. It is not uncommon for the CR job that serves them to leave cars sitting on the industrial, although they usually leave them on the runaround down by the bank in Harrison (behind the former Hartz property). I don't know exactly where on the industrial the 18 is sitting, but I imagine it is down by the runaround if it was west of Hudson. There have been two tank cars sitting on the runaround, the two that are coupled to the 18 might be the same ones. If there was a multi-level car sitting east of it, that would explain why the SK job left the cars, and the 18, there rather than taking it all with them.
Proven Theory #2 - If you don't work for the railroad, you don't know more than the people who do, no matter how many years you've hung around the tracks, or how well you think you understand railroading.
Rest in peace Jtgshu.