There was a similar sort of question asked by a 3D World reader a while ago, in the Q&A section. I don't have the article in front of me right now, but I remember the answer involved creating a crack (or incision in your case) in the surface and then creating polys to fill in the gap. Dynamics were then used to control the way the pieces fell.
Not totally relevant to your problem, but I would think you could use something along the same lines.
I'm sure there are better and easier ways of doing it, but as I'm a newbie, I don't know. Somebody who has more experience with Maya will probably have a better suggestion.
Good luck with it, anyway.