Having watched:
http://wordpress.tv/2013/08/07/john-james-jacoby-beyond-the-blog-with-buddypress-and-bbpress/
About 30 minutes 30 seconds in it says that it is possible to run multiple and unique buddypress installations on a network. What I haven’t managed to workout is if I had a central wordpress information site that requires log in, for example mydomain.com, would it be possible to run multiple subdomains of cbox (e.g. dept1.mydomain.com, dept2.mydomain.com, dept3.mydomain.com etc.) each with their own privacy from the other cbox installations/subdomains but all with the ability to access the main central site (mydomain.com) without having to re-log in? If it is possible, does any one have any recommendations on the best way to go about this?
.
.