I have Exchange 2013 setup following the hosting guidance documents provided by Microsoft. We have several companies in our umbrella, so this design makes the most sense. The one issue I have is that we have three domains ("Tenants") who work out of the same physical office, and share a single physical conference room.
I need a solution to setting up a room mailbox for this conference room, and have anybody from each of the three companies access it for scheduling purposes.
With the EAB policies and access to each other's GAL denied, I am not sure how to resolve the issue.