Dobber78,
I don't think I have ever seen one paved for higher Voltages. I am not sure why you would want to. Paving implies rebar, wire mesh, etc..., for concrete strength and to limit cracking. I don't know how you would calculate the step potential for reinforced concrete at a switch or transformer. At lower Voltages, I have seen them, but many of those used enclosed gear with grounded enclosures.
EEJaime