NYC engineers of steam engines

Rattler,
That is not the way things worked at all.
First, one had to start out as a fireman. He would start out making qualifying trips until he was proficient enough to be marked up on the extra list. He worked the extra list filling open positions where a fireman on a regular job was off for some reason. He would work the extra list most likely for a  number of years before he had enough seniority to hold a regular job. 

In this time, he would have worked on many different types of locomotives . The type of locomotive depended only by what the Roundhouse Foreman decided to put on the train. You didn't work on one type and then move up to another type. You worked on what loco was dealt you for that particular trip. So, after many years as a fireman on many different locos, the day came when you were promoted to engineer. Then you started all over again on the extra list. 

As for where one could work, that depended on the local union agreements. Where I am from [ not the NYC ], Yard men stayed in the yard and Road men stayed on the road. We were hired onto one particular seniority district and for the most part stayed there. If you wanted to transfer to another district, you lost your seniority on the previous district and went to the bottom of the seniority list. Just like brakemen, there was the provision for a fireman to work "emergency" on another district if that district had used all of the men on the extra list and needed someone to fill a vacancy for that one trip.

I would think others here have/had different union agreements too.
I wouldn't have cared for yard work and I really didn't care for the turnaround locals as I didn't care for shift work and an alarm clock. I still can't sleep if I know an alarm clock is set.

Pre-Amtrack passenger service was a bit different as the train crews could cover two seniority districts, but, the engineers did not.

Then, well into the diesel era, interdivisional runs for T&E became more frequent depending on how the company wanted to run trains.

Wyhog posted:

I'm glad we didn't have separate yard/road engineer seniority.

We didn't where I worked either (Santa Fe Los Angeles Division).  Santa Fe had four Grand Divisions: Eastern Lines, Western Lines, Gulf Lines, and Coast Lines.  The Coast Lines Brotherhood of Locomotive Engineers labor agreement was the only one of the four that did not have separate Yard Engineer seniority.  By the time I was transferred to Texas (1993) they had combined the two lists resulting in two top and bottom lists where former Yard Engineers were listed ahead of former Road Engineers and Engineers promoted after the combining date, for yard assignments, and the reverse was true for road assignments.  There were only three former Yard Engineers still working at Slaton . . . and all three worked on the road!

Until the late 1960's the Gulf Lines, Southern District even had a Jim Crow seniority list at one terminal: Sillsbee, TX.  All Firemen were "colored",* and could not be promoted to Engineer.  All Engineers were white "hired Engineers," experienced Engineers hired from other seniority lists, and sometimes from other railroads, although preference was given to promoted Engineers from other Santa Fe seniority lists.

Separate yard and road Engineer seniority seemed to be prevalent in the South, but existed elsewhere.

* Archaic terminology in this age, but that was how the railroad officially referred to black employees and patrons.