Star Wars - Episode III.V - Rebellion Ascendant
The HoloNet during the Rise of the Empire Era is used strictly for military purposes. Major military installations and large population centers might sport a HoloNet node in their Imperial Facilities to which access is restricted to the highest ranking personnel.
The major point of HoloNet use, however, is in Star Destroyers. Considered Standard Issue in all Imperial-I class and above, and with an ongoing attempt to refit the older Victory-I and Victory-II classes, the HoloNet allows almost-instant communication – and thus coordination – of the numerous Imperial Fleets in the Galaxy.
As strict Imperial Policy, Hyper-Transceivers are not used in older classes of ships than Victory-class, as a single transceiver in a fleet group is enough for the entire fleet to utilize it and a Star Destroyer of some sort very often acts as the flagship of a fleet.