The compass isn't really an issue when flying VFR doing pinnacle approaches to tall stationary objects, and hover work. In fact, it's the last thing one might reference.
The potential between the helicopter and the wire is achieved by bonding before the transfer of the worker from the helicopter platform to the wires, and then again before returning to the helicopter again. With the potential adjusted, there's no risk to the helicopter because there's no ground from the helicopter.
If the helicopter had a ground to earth, such as a rope or chain hanging from the helicopter to the ground, that would be another matter completely.