Hi Emma
The answer to your question can be found in Part 2 of the Government Telecommunications Act 2018 (NSW). https://legislation.nsw.gov.au/view/whole/html/inforce/current/act-2018-067#pt.2
The NSW Telco Authority is constituted by, and functions under, the Government Telecommunications Act 2018 (NSW) to operate and maintain mission-critical operational communications services for public safety and government agencies within NSW. The NSW Telco Authority holds responsibility for coordinating telecommunications services support during emergencies under the State Emergency and Rescue Management Act 1989 (NSW), has a central role in coordinating spectrum holdings on behalf of government agencies and manages major digital connectivity programs for the NSW Government.
Based on this information I would suggest that rate assessment would be exempt from rates under section 555 (1) (a) Land owned by the crown, not held under a lease for private purposes, as the activity fits the function of the Authority and is not being used for private purposes.
Anthony