How do they keep vegetation clear from underneath high voltage power lines across the entire continent?

Question

I mean how many men does it take, do they work all year, how do they get in and out of remote areas?

Answer 1

Geese.

Vast flocks of highly trained, grass-eating geese.

Answer 2

Most high-voltage transmission lines have access roads underneath them. Those that do not can be accessed by helicopter. They are regularly patrolled by small aircraft so that they know when clearing or maintenance must be done.