There are very few render engines that can render a NURBS surface, the vast majority have to convert the objects into meshes. Does Simlab ask you to set a Tessellation parameter or a smoothing amount. If not then it's either using its own default settings which it considers good for all or it really is rendering the NURBS surfaces. The best way to test this is by doing something like a wheel and then zooming in, if you then render the view and you can see straight lines forming the illusion of a curve, then it's most likely using a render mesh.