Well, APEX D version I saw has an option to represent smallest chunks as GRB, but it was not working.
Currently, GPU Rigid Bodies were used only in Batman Arkham Asylum, and there is great article about it, called
"PhysX GPU Rigid Bodies in Batman: Arkham Asylum" published in Game Programming Gems 8 book
Aslo, there is presentation from SIGGRAPH 2010 - "Collision detection in PhysX" by Richard Tongehttp://tclab.kaist.ac.kr/~sungeui/Collision_tutorial/Richard.pdf
which states that rigid bodies used in Batman were designated as GRB 0.9, and more advanced GRB 1.0 system is in the works.
However, I have no information if it will be includes in SDK 3.0 or not.