But a spokewoman for Optus said the damaged infrastructure was an abnormally large 4G booster, and not a 5G transmitter.
“Optus is working with local authorities to investigate this incident,” the spokeswoman said.
“We take vandalism of our infrastructure very seriously as customers and businesses rely on our services, now more so than ever.”
Police said they had inspected the pole and determined that it posed no risk to the public, but the fire was deemed suspicious and officers were investigating.
Telecommunications is a vexed issue on the harbour view side of the Vaucluse peninsula. The signal used to be so poor that residents had been forced to hang out their windows and walk onto their decks to make and receive phone calls.
One resident said that she received her signal from Mosman, on the other side of the harbour.
The Morning Edition newsletter is our guide to the day’s most important and interesting stories, analysis and insights. Sign up here.