I have had a lot of experience trying to get CAD files correctly registered in Manifold 8. In Washington State, a CAD file could be projected to Washington State Plane North or State Plane South. The datum can be NAD83 or NAD27. Units of measure can be in feet or meters (typically feet because we Americans are mired in the illogical Imperial units of measure). It all depends on where in the state the survey was conducted and how the base monument was located by the local jurisdiction. Sometimes (fortunately not often), a survey could be in Universal Transverse Mercator Zone 10N. I will go through the most likely projections until I come across one that is reasonably correct based on the Lat-Long on the status bar. It would be nice if the surveyor would provide projection information on their files. Mostly, they don't.
Things get really interesting when the survey is based on pseudo-coordinates. Surveyors will often get a CAD drawing out that is dimensionally correct, but not projected. The CAD files can be projected at a later date if needed. When I get a file using pseudo-coordinates, I end up having to manually georegister each layer. I will register one CAD layer to a GIS drawing layer that contains the same information (such as a parcel boundary). Then, I will use the newly registered CAD layer to register all remaining layers. If I were facile in writing scripts, the process could be automated to save me time.