I just ran across this topic and thought I'd jump in. When Steamtown moved from Vermont to Scranton, the Big Boy moved -- a lot. I live near the D&H line in Nineveh Junction, NY but was at work in Binghamton when it came through. I would have loved to see it crossing the Harpursville trestle. I was working at Universal Instruments in Binghamton next to the Bevier Street yard. I had a scanner going and my Mom and Dad were calling me with progress reports. It arrived in Binghamton around lunch time so I went out to greet it. It was stopped at the entrance to the yard, just past the Bevier Street overpass. I got to get up really close - close enough to touch it. I waited until it moved out, huffing and chuffing as the pistons pumped air.
I assume a lot of work was done on it to get it ready for that long move.
I have a photo of it on the Nicholson viaduct that a friend took.
Back when it was in Vermont - in the early 1980s as I recall, I got to sit in the engineers seat and pretend to know what all those valves, gauges and levers did.
When the NPS initially took over the Steamtown operation there was some talk about doing a partial restoration so it could move under steam again. The plan (as one to the rangers explained) would have been to get to boiler up to a state where it could operate at reduced pressure and have one set of cylinders operate. They figured it would draw a huge crowd from all over the world to see a Big Boy move, even very slowly, under steam. As I recall the cost was pegged at about a half a million to do just that limited work. As I recall that idea was shot down by political forces quite quickly. If I recall correctly there was a specific restriction put in to prohibit funds from being spent on that.
This is all stuff I heard around the park in the early days and may just be based on someone's pipe dreams, but it would have been nice to see come true.