Before the streetlights along Milk Street give up for the morning, there is a truck out with its blade down. Alberto & Sons Landscaping works the driveways and walks of Westborough in winter, salting the slick spots where cold settles low near the headwaters of the Assabet. Come the green months the same routes run again, this time for mowing, edging and trimming, with spring and fall cleanups to bracket the year. There is a particular satisfaction in a driveway opened curb to curb and a lawn whose edge holds a straight line all the way to the mailbox. Neighbors step out, take it in, and go on with their day — which is the whole idea.