We have a similar system over here in NZ for washing insulators and also testing the integrity of joints in Live 110 and 220kV transmission lines.
The guys that do this sort of work are of a breed, all thier own.
The system is called a Flying Work-bench and the line mechanic sits out on a platform attached to one of the skids on the chopper.
The line mechanic wears a suit that is bonded to the Line under test.
The helicopter is also bonded to the line,
(this is a specially made chopper that has extensive bonding and isolation as part of its structure, because of the severe Eddy currents, from the Line, which would upset the instruments of a normal machine, not to mention, vibrate it to pieces).
A test jig is then connected to both sides of the joint and the voltage drop across the joint is measured by a guy inside the chopper(not the pilot!), with a lap-top.
Bear in mind, that sometimes the main rotor or the tail rotor of the chopper may be as close as 100mm(4") away from the nearest line or insulator, you would hope that the pilot was not thinking of something else.