My former employer, CHL, does a similar thing in Canada but not with a platform. They use an integrated tool system where the aircraft has a tool attachment on one side (basically a giant hook) and a counterweight on the other. They call it Helinas. The attachment hooks on to a man-carrier, a tool basket, or a trolley. The TwinStar hovers next to the appropriate basket or tool and slides in to hook up, then carries the load up to the powerline where it places the load on the wire.
Very slick system, and the guys who fly it are serious pros.