Extracting three different masks from a texture's rgb channels

[Joezeta]

I need to apply a Vray blend material with three submaterials to an object. Each material need to have its own mask. But I need this masks' file to be the same, to export it in a game engine.
So basically I need to Vray to read data separately from each r,g b channel, so that each channel behaves as a usual black and white mask. Is that possible?

[Pixelcon]

I think the standard RGB Tint map is the easiest way to do this...