The rotary in action.

The rotary in action.

History and operation.

https://en.wikipedia.org/wiki/Rotary_snowplow#Power

As stated in this description, While all rotary snow plows had engines to power the blades, only some of them had secondary engines to propel the unit.

Southern Pacific Upgraded

Their rotary plows in the late 50's by changing the power for the rotary blade by using two diesel traction motors  geared to the shaft and then using an F7 B unit as dedicated power for those motors with wired connections to the snow plow. This in turn was pushed by whatever was the preferred power of the day. Cab Forwards in the steam era. SD-9s became preferred after steam  They  were operated in sets with rotaries facing in both directions so they could extract themselves in case of an avalanche This was the Donner Pass operation.

An interesting book to read is "Snowbound Streamliner" -Signature Press by Robert Church. He gives a very thorough accounting of the circumstances leading up to and the problems of rescuing the passengers and in extracting the snowbound City of San Francisco during the winter of 1952.

Espee over Donner