Andrei,

I'm not sure what you mean here ...

I though the advantage of T-Splines and PowerSurfacing (PowerNurbs) is that you had a nurbs model that could be edited easily using the polys.

I used PowerSurfacing plugin in SolidWorks. If I wanted to change the shape of the nurbs model that is generated, I just edited the polys as I would in most poly modelers. At least that's how it functions in SolidWorks.