In this case, it's a walled-off Facebook about work. You can use all Facebook's tools to communicate with your coworkers about things you're doing at work, without making it public.
That happens already, with share to group which happens to contain friendly coworkers. Only difference is linking it to corporate active directory such that we won't be able to share to "work friends" group but will have to share to the whole department. Probably lower overall use, possibly because of negative gossip but also self censorship in that I know the work office cooler club or whatever all talk about minecraft, but I'd think twice about having to spam that to the entire department not just the people who are into it.