The simple answer to that question is, no.
It does not work
Vray materials dont even show up as blackness or alpha black on the render screen
But you can do render passes. You will have to convert your vray materials back to standard or mental ray ones
So does anyone know of a way of converting Vray materials to Mental ray materials?
And back again?
I have seen the script to convert standard materials to Vray,
but nothing that goes the other way.