Ann Arbor's plow truck fleet is out in force in the wee hours of Sunday, 15 December 2013. You can follow along your self on the city snow plow tracking page.
No, I don't know either why Jackson Road is labelled as US-12. More details of the City of Ann Arbor plowing program at http://a2gov.org/snow.
How much snow did we get? The National Weather Service map says about 6 inches in Ann Arbor.