They sort of a hybrid. Caltrans has plows that combine horizontal helix looking rotary plows
with an ejection wheel much like a railroad rotary. I've seen some Swiss pictures of just such a
unit mounted on a small flatcar. Plasser I believe builds these in Europe as a standard product
though with European train frequency (and tunnels)snow isn't such a problem. There's notations
that snow wasn't a real problem on Cumbres Pass until the daily passenger (The San Juan) quit
running. If you have enough and then let it drift in you're going to have problems.