I don't see why he thinks there will be interference even on 72. The power being transmitted on the power lines is low frequency AC. I would think the power co would not permit any discontinuities that would generate high frequency harmonics.
You may get reflections that will seem to be interference especially on 2.4 if your aircraft is setting on th ground. Test this by moving your aircraft a couple of feet and see if it gos away.In the air it would fly through them so fast you would not notice them.
200' is far enough away that you would not get magnetic coupling. I would suggest that you do not fly on the side of the field the wires are on.