Many of them are "annulled." It is a simple term on our railroad meant .............it doesn't run that day! Not sure what you mean, but if you are thinking the trains are "parked" as a "set" and sit there, that' doesn't happen. (AT least I never saw such & it wouldn't make sense! Trains are made up at originating stations according to schedule and need. They are made up according to a "work order" and the number of cars that would be in the consist. If they aren't to run, then the cars simply sit in whatever yard track until call OR a switcher will pull these cars and spot them on a designated track for pickup according to the work order. At the right time (whatever that may be), they will be put in a track for the engines to pick up. Trains consists CHANGE as the train preceeds over the route, setting out cars for industry at one station, picking up loads and "MTYS" (empties). then its on to the next station where the process repeats itself. IF it is a special train, like a dedicated FRUIT EXPRESS or a "just-in-time' consist like Triple Crown, there are FEW, or NO, stops. Like the railroads, the originators work AROUND the holiday so that only ESSENTIAL shipments go out.
Most scheduled employees, except for the most essential ones are OFF for that day with pay, and Extra Board employees are called off the 'board to work the assignments (Yards, switchers, clerks, etc) The switchers that ARE working that day will make up any trains so as to ensure the train WILL be ready for call during its next shift. BUT! the next day (after Christmas, for example) COULD begin at twelve naught one the 26th as that is a new day entirely and the assigned crew called to protect. During that day of "annullment", there are "skeleton" crews on duty on all shifts at each yard----maybe as few as 2-4 people. Maybe this helps some.