Behind the mill brick of North Billerica the old Middlesex Canal still lies in its cut, holding a strip of sky. K.A. O'Neill Landscaping & Snow Service keeps the yards on those narrow village streets — mowing, trimming, the autumn leaf haul that turns a lawn back into a lawn. Winter here is close quarters: short driveways, granite curbs, and a foot of snow that has to go somewhere sensible. The crew plows and shovels and salts until a door opens onto clear ground, which is the whole point of the exercise. Billerica and the towns beside it get the same attention on a Tuesday in July as at two in the morning in February.