Standard practice on HT conductors in New Zealand is to earth the HT wires at both sides of the worksite, after the lines are proven de energised.
I take it that this standard is adapted by most POCO's around the world.
Even if someone with a 5 or 10 kVA generator tries to backfeed the grid, the existing load will absorb this amount and the generator will trip on overload or stall.
As per normal working procedures PPE is mandatory, harness, safety goggles, hardhat, full body cover overalls and insulating gloves rated at the HT voltage on the line during maintenance.
Of course care is always needed in case of backfeeding from an other source during line maintenance.
