Private car participation in the display at Washington Union Station and Philadelphia 30th Street Station may be limited this year, as Amtrak has changed the "rules of engagement" for this event.
In the previous years, Amtrak asked the owners of Amtrak certified PVs if they were willing to display their car and make it available for public walk-through tours. The car owner provided the car to Amtrak for that purpose without any charge to Amtrak. In return, Amtrak provided a free move from home to WAS or PHL and return, along with free parking at the station for the event.
This year, Amtrak's Marketing Department has no budget for this aspect of NTD, but is asking PV owners who may be interested and willing to participate to pay all of the standard tariff costs (mileage, switching, parking, etc.) of getting their car to the display city, parking there and going back home after the event. At the moment, I believe there will be only 2 private cars (CANNON BALL and DEARING) on display at Washington Union Station for NTD 2014.
I don't know about Philadelphia, although Juniata Terminal Company is only a switch move away from 30th Street Station.
Los Angeles should not be a problem, as there a number of private cars parked at the Garden Tracks, a very short switch move from Union Station.
I'm not sure about Chicago Union Station. Several PVs are stored in the yard at CHI, while the nearest other private cars would be based in Milwaukee and St. Louis.