Well you know, preparing a cage object for zbrush means 'avoiding' (not sure for the spelling) anything that is not quadrangle. You can mix triangles and quad in some area (if there is no alternative), but it's better to avoid it. Surface subdivision don't work really well on that kind of geometry, and gives bad topology for sculpting anyway.

I don't really see the point of using nurbs, of meshing object from nurbs, for softwares like zbrush. There are so many rules to follow when using poly modeling to create a good low-res zbrush friendly cage object, that I can't imagine any meshing tool clever enough to create it.