The Providence & Worcester, pre-merger, ran a regular program of excursion trains, and being primarily a freight operator didn’t have any power that provided HEP power. So they purchased one of Amtrak’s heater cars – ex-AMTK #456, rebuilt from an E9B – to provide hotel power to those trains.

After the merger, new HEP equipped class DP2 electro-diesels supplanted X668, so after kicking around the system for about a decade it was remanufactured into a DL50 b unit for the LT&L official train.