Trying to get the sl-king link installed for KML files at the moment as pre this old post with no luck. Is any one using the link in Civil3d 2014? May just convert the Kml files to shp files and do it that way.
http://www.atlantic-cad.com/2014/11/03/civil-3d-fdo-provider-for-kmlkmz/
http://cadandgis.blogspot.co.nz/2009/06/autocad-map-3d-connect-to-arcsde.html
http://cadandgis.blogspot.co.nz/2009/06/autocad-map-3d-integrating-autocad-map.html