The Intelligence bureau was a part of Imperial Intelligence that would take the data from the Analysis Bureau and run it by a group of experts to predict what the Empire's enemies would do next.
ExComm relayed messages between the various branches of Imperial Intelligence, the Ubiqtorate, and the Imperial military.
These branches were specifically assigned to perform intelligence activities in their designated sector.
This branch predicted trends of groups that offered resistance to the Empire.
This branch was formed in times of crisis out of experts from the other branches. It would be under the control of the Ubiqtorate, but could also answer to a Grand Moff or the Emperor himself.