Box fill calculation for isolated ground receptacles
I worked in a hospital back in the late 90’s early 2k. I still have notes in my code book pointing to 250.146.D with a note that states isolated grounds count as +1x the wire size, I jumped back and read it and today it is not clear. But since it is a separate means of grounding I would count the isolated grounds as grounds but separately from the required grounding. This would mean in that box a 2x total count for grounds where 1x the wire size is normal. An isolated ground can pass through a box or panel without being connected if not used in that box or panel. The isolated ground will be bonded at the service panel for the building. 

Hope that helps , it is fuzzy but I know it was required so I would count it.