Yes, they are typically either opened or closed. Depends wholly on the school nor should an interview in a group really have anything to do with the info in your file. They are trying to see you interact with others and your own social / interpersonal / communication. So if it is open file, they already know about your so trying bring info up that's in your file is pointless. If it closed file, they have purposely set it up so the info in the file is irrelevant to to the discussion. Bringing anything up from the file would then seem like you are simply trying to bolster and impress.
So in short, it is almost wholly irrelevant to an applicant in group setting whether the file is opened or closed