CoolHand posted:If the postwar ZW is on a completely separate circuit (lights & accessories) than the modern ZW (track power) why would it be beneficial to phase them? What did I miss?
As noted, "it" happens. If your derailed cast hopper hit's the metal base of an accessory you'll be happier if those commons are in phase.
Plus many accessories interact with track too. It's best to approach this as a "just do it" rule of thumb Once you have a few plugs marked it pays for it'self in piece of mind.