Let's say a private individual wanted to pull a Ross Rowland and buy and operate their own locomotive (diesel or steam, doesn't matter). What all would they have to do to certify themselves to operate it and what would they need to do to operate it on roads?
Just because you own a locomotive does not mean you can operate it.
Most Contracts and rules will let you run this engine with a pilot, with a rule stipulating that pilot must operate the engine.
Only reason a guy like Ross Rowland or Doyle McCormack can operate their steam locomotives is because 99.9% of all engineers are not qualified on steam locomotives.
So they still get a pilot but Pilot will not operate the engine.
Doyle McCormack and others who restore diesels, will find they get no time in seat, as Pilot will operate the train.