I have a viseo someplace that shows a professional crew setting up for that kind of shot in the Chama yards. It was the day after the season ended and they had chartered 497 to push OM up to Lobato and return.
The put the camcorder on a nearby track and ran a long cable under one rail to the ens buried in the ballast. Everything went OK.
The danger with putting the camera in the ballast is not the clearance but the heat from the firebox - heat tends to destroy anything plastic or electronic it passes over. Anything consumer grade anyway.
Doug vV