Free Busy is working for users but the Rooms or Resources can not be booked and the following error is return in the CMN log: "The specified email address was not found"
This is caused by the contacts being hidden in Exchange. The contact objects were created in Exchange and then hidden. This will manifest it self when you come to select the object from the GAL when trying to book a meeting.
Unhiding the resource allowed mail routing to work and the Meeting to be booked for the hidden resources