I interpret "Running train in the snow" as running trains when it is active snowing and or plowing of snow is needed.
Running trains after the snow has stopped and has been cleared off of the tracks is simply running trains in the cold. In the cold both scales have to be mindful of how the cold will affect the materials, especially making plastic much more brittle, but electronics will probably not be affected unless they are stressed by taking them out of a warm house into bitter cold then back into a warm house. My G scale was stored in a unheated shed.
When I open up an O scale engine I see it full of electronic circuit boards with tiny components on them. Circuit traces are very thin and therefore appear to be more fragile. Electronic reverse boards are basic in most every modern O scale.
Opening up a G scale engine you'll most likely see circuit boards with thick electrical traces, larger but more basic and robust components. Track powered G scale doesn't need any reverse running circuitry, you just change the polarity to the track.
Granted, I'd never run my G scale Blue Comet with smoke, full sound and remote control with detailed passenger cars in any kind of foul weather. I always chose basic locos that I was sure could handle damp conditions. (only a couple were allowed to go out and play in bad weather)
I hope to have a small O Scale outdoor layout some day but it will be strictly a fair weather layout. None of my O scale equipment will be allowed out to play in the snow.
