It's fascinating how the different software tries to tackle this problem.

In ViaCAD Pro there's a tool to Untrim a surface. So after converting a solid of this test part into surfaces (which remember destroys the original integrity of the nice ACIS produced patch), I Untrimmed this patch and like BurrMan did, switched on control points.

The result is in the picture which to my eyes looks a mess and surely not what I would expect ACIS to produce.
A 3dm file version is also attached.

I hope this discussion helps Michael to engineer a good solution from it all ;)

 

Martin (2).