The fire brigade was called to the mobile phone tower near Parnell Court shortly after 1:30am on Friday 21 May.
The fire was extinguished, and Arson and Explosives investigators attended the scene later than morning and deemed the fire to be suspicious.
Police have released an image of a Holden Commodore sedan that was seen in the area prior to the fire.
The vehicle was driving without headlights on in the vicinity of Parnell Court and police are keen to identify the driver or registered owner of the vehicle.
Counter-Terrorism investigators are continuing to work closely with detectives from the Arson and Explosives Squad.
Should the investigation reveal the fire was a deliberate act, police will view the offending as a potential sabotage offence targeting critical infrastructure.