Celtaddict,

Many thanks for that. In the UK the people who maintain the track are called 'platelayers', a term which goes all the way back to the birth of railways and the iron tramways which preceded them.
There are, of course, many thousands of railway/railroad songs but not, I imagine, very many about track workers (Dave Goulder sings a couple on 'Requiem For Steam').
Incidentally, if there should be any lingering doubt as to what a 'jimmyjohn' is, a quick search of Youtube will settle it.
There's one clip, taken from a feature film, in which Frankie Laine and his troupe of dancers dance around a giant 'jimmyjohn', a large earthenware 'moonshiners' jug, which is part of the studio set.
Frankie then jumps on top of said 'jimmyjohn' to finish the song.
This has to be considered pretty conclusive evidence.