Could these have been orange, maintenance of way hoppers? Similar to this?
http://www.rrpicturearchives.net/showPicture.aspx?id=1385473
A hi-rail truck rolls by, and via computer, will determine how much ballast is needed at a particular point. This information is transferred to a later ballast train. Each hopper has a computer and power supply (solar panel) on it, and will dump the right amount of ballast at each location. People are still needed to monitor it, but not quite so many as a regular, manual ballast dump.
I think I've seen photos of BNSF cars like this, and probably other Class 1 railroads will have them also.
Trains had an article about these, sometime within the last couple years.
James