About 2013 I completed something similar in the UK and gained EASA STC approval. It has a HEC with two people in a basket specifically designed for 'live line working'. i.e. the guys in the basket carried out maintenance/repair work on live high tension power lines. All whilst the whole lot dangled from a hovering AS355NP.
In this instance we had to do a lot of work to prove that the people and basket were electrically isolated from the helicopter. The complete opposite of what you are being asked. We used high dielectric 'ropes'.
The aircraft was/is limited to 'Day VFR' with the rig installed.
Not sure that helps you though...