The short answer
Responsibility is shared. The network operator typically manages vegetation clearance around the public network lines. The property owner is generally responsible for trees on their own land, including trees near the private service line that runs to the home.
Why the rules are not the same everywhere
Each state sets its own legislation, and the rules shift with the type of line and where the tree sits. A tree touching a public line is treated differently from one leaning toward a service line. Owners who ignore clearance rules can face fines, and network operators may trim or remove threatening trees, sometimes without notice.
Nobody should pick up a saw near a powerline until someone has worked out whose line it is and whose tree it is.
Joseph Khoury, Director & Founder, Trees Down Under
Get it assessed before work starts
The safe move is to have the situation looked at first, whether that leads to pruning or tree removal in Sydney under a council permit. Trees Down Under works out who does what, then handles the paperwork and the work. Call 0475 463 597 any time to arrange an assessment.