Can the Intel IG work with the GPU?

As I recall, this is essentially what the Lucid VirtuMVP program does. It offloads some of the graphics processing to the IGP, which the IGP can do fairly well (like background textures and the like), freeing up the GPU to do the more complex things, or functions the IGP doesn't have like T&L. I think right now it's pretty limited in the configurations it supports, so you'll want to do your homework ahead of time.