I worked for a construction company and spent most of my time there on rail rehabs in and around NYC- Amtrak, LIRR, NJ Transit and Metro North (minimal), both on site ad estimating. The basement of Penn Station is kinda cool, happy to say I have been there, but I don't need to go back.
After leaving NYC I worked for an engineering company that was starting a construction division/group in the Denver area. We had some construction projects regarding railroads, primarily a lot of bidding but we did rebuild one bridge in Iowa for CP (I think, maybe it was CN). I also had water/dam projects in the mountains that use the old rail tunnels for water transfer. That was pretty cool to see.
After that I worked as a consultant cost estimator for Denver Regional Transportation District (RTD), about half my work was rail related.