I was under the impression that any fixed wing plane with the president on board automatically assumed the designation of Air Force One.
No matter what its normal status was.
Similarly for Marine One as long as it is a Marine Corps Helicopter.
A number of railways around the country and also some engineering firms do work of this nature.
The Railway works tend to make use of spare capacity to do contract work.
The engineering firms are in it for the work.
In nearly every clip you can spot workmen standing / sitting idle using phones or other devices.
Some may be official but I doubt all are.
In any PTS I thought all phones should be off unless required.