This is way outside of my circle of insider information so treat this as any other internet post. The steel Lackawanna coaches are really the only candidates for possible use in a train. Decent condition, mechanically sound, working brakes, etc. This is way too short a notice to consider any other option. And in fact we are all waiting for a waiver from FRA before any schedule of actual train service can be announced or implemented - the last I heard.
The original plans for the locomotive were surely as a wood burner. It is currently equipped to run as an oil burner.