That`s how I created this (right curve). I used that line tool manually but If I have 1000 lines like this to rebuild whole subd model then it will took ages and I may make mistakes often.

I`m asking about automatic way of doing this on 1000 curves. Next I would rebuild surfaces from those curves in MoI3d.

If 3dm file would be a text file then I could write python script to change that polyline curve to nurbs curve with same vertex->points position.
I know there is scriptingin MoI3d but I don`t know it :)