Oleg's team had a tech demo of their own physics engine back in 2005. If I recall the reports they had barrels being knocked by blast waves and then rolling into wire fences and bouncing off of them (the wires acting like elastics). I doubt we'll see this type of detail in CoD, but I bet the engine can handle it.

It would be interesting to find out if there are real technical barriers to offloading physics calculations to the GPU, given that Oleg is using his own physics engine.

From what I've seen and read, neither PhysX or Cuda will be utilized. The fact that there's still some question about it also confirms it won't be utilized, as it's something that surely would have been made known by now if it were to be implemented, and it would actually contradict some other things that have been made known.

About CUDA though, if you're using Adobe Premiere Pro or Photoshop (and perhaps After Effects, I'm not sure) for your movies, then going nVidia would be a good idea, as they do make use of CUDA to speed things up quite a bit when editing.