At the moment the snow effect is a child of each model and can be edited out in the bin file. I can add snow to the trucks but the effects would then need to be a permanent part of the actual model. I did that with the RS3 when I was experimenting. The effects would still only show in the winter and could be turned off.
As things are at the moment if a user wants to remove the snow permanently they can. Also doing things this way I can add snow to models I have already upgraded and supply them as a "Winterisation Pack"!!!!!!!

(Slightly less work for me.)
Dick