How are engineers protected against lightning strikes when testing transmission lines?
Maybe it is more safe on a transmission line tower than standing on earth because of the following reasons: 
1) A standing person is higher above ground and is more likely to catch a lightning strike, whereas on the tower, the lightning will always hit the tower first. 
2) A iron tower is a better conductor than earth, which leads to smaller voltage drop per distance at the same lightning strike current (U=R x I)