Well the mystery is partially solved. This was done in preparation for a recycled-in-place first course. They have a huge train of mill, water tanks, asphalt oil tanks, mixing machine of some type, etc., etc., etc. They are milling several inches deep, going through all this machinery and placing it as a base course for a final overlay. I presume the initial micro milling was done to get rid of the chip seal and whatever garbage was in the traffic lane? Now it is definitely for sure that the DOT was wasting time and money doing crack sealing before this since the cracks are getting ground to powder along with everything else. Oh well.