Hi, my team and I have search for this too, and we finally got a response by e-mail here what they say:
"The Geometry API only works with low level 3D channels, Studio API uses the 3D panner DSP which doesn’t currently include geometry occlusion. We recommend creating an “Occlusion” parameter on your event which controls a volume and/or lowpass automation, then driving that parameter using Unity’s ray casting to simulate occlusion. This offers the benefit of not duplicating the geometry data inside FMOD and using the engine’s inbuilt raycast algorithm.
Here is one example of how it could be implemented:
http://52.88.2.202/questions/question/forum-40283"