AutoCAD Map 3D comes with a grid data catalog file (RgfToNtf.gdc) and a national grid data file (gr3df97a.txt )for France. This file is installed in a folder under the Autodesk shared coordinate system folder, by default C:\Documents and Settings\All Users\Application Data\Autodesk\Geospatial Coordinate Systems.
Several French municipalities have developed local grid data files that allow for more precise transformations within their respective regions. You can obtain municipal grid data files from the local GIS or Survey department. If you add references to such municipal grid data files to the French grid data catalog file, AutoCAD Map 3D will automatically use them as appropriate. Points within the boundaries of the municipal grids will be transformed using the local grid data, and points outside those boundaries will be transformed using national grid data.