I have done fires and I work on energized lines, it is impossible to get a jolt in the helicopter. The lines can flash if the water provides a path from the phase to the ground or earth/shield wire to phase but the helicopter is not earthed and is therefore not in danger from the flash-over. If it was, your colleague would not be alive to tell the tale.
For the pilot, the worst case scenario is getting the bucket caught, for the guys on the ground it is the water providing a path for the current to flow which will result in a HUGE bang and a secondary fire. Dense smoke does the same thing as water and can create a flash-over risk.