February in Woburn comes in sideways off Rag Rock, the hill flinging wind down onto the streets beneath it and packing every driveway apron tight. Black Diamond Landscapes, Inc. is out in the middle of that — plowing, shoveling walks, running salt through the small hours so morning can look unremarkable again. When the ledge finally lets go of its last gray drifts, the trucks come back with mowers and the year turns to cutting, edging and cleanups. A lot pushed clean corner to corner, nothing left ridged in the wheel tracks, is the sort of finish you can see from the road. Woburn's hills make the work heavier and the result that much plainer.