From T&DWorld:
“That’s crazy!” “That will never work.” These were the reactions of most utility personnel when the idea of side trimming trees by suspending a device with ten whirling saw blades under a helicopter was presented to them in 1985. At that time, most side trimming for electric utilities was done by climbing crews or mechanical trimmers working from the ground. Most utility vegetation managers were skeptical this concept would ever work.
From YouTube:
Helicopter to trim trees? Check out this segment on a contractor, unreachable power lines from the most unlikely of places.