Hi!

Its rendered with Maya software, simple anisotropic shader setup!

Why cubic and linear?
Because it looks like an offset tool doesnt work best with rounded shapes on one and corner shapes on the other side!
The only way to produce sharp corners with cubic curves is to put 3 CVs on the same spot wich causes problems when offseting and lofting!
I dont use curves very much and now I am punished! :-)

Do you mean I should convert thoes surfaces to polys or subds?