http://www.legislature.mi.gov/(S(ms52dfvh1qq2oo34eawymj13))/mileg.aspx?page=getObject&objectName=mcl-257-653aHere is the Michigan law. You are required to either move over at least one lane, or if movement to an adjacent lane or 2 vehicle widths apart is not possible due to weather, road conditions, or the immediate presence of vehicular or pedestrian traffic in parallel moving lanes, the driver of the approaching vehicle shall proceed as required in subdivision (b).
(b) On any public roadway that does not have at least 2 adjacent lanes proceeding in the same direction as the stationary authorized emergency vehicle, or if the movement by the driver of the vehicle into an adjacent lane or 2 vehicle widths apart is not possible as described in subdivision (a), the approaching vehicle shall reduce and maintain a safe speed for weather, road conditions, and vehicular or pedestrian traffic and proceed with due care and caution, or as directed by a police officer.
From your description, you are not guilty. I would go to court and plainly and without any emotion state exactly what you stated here. This is where a dash cam would be very helpful.