Are you Canadian by any chance? It's common in Canada to call electrical utilities "hydro" whether there's water generation or not. In the states they don't do this as much. At least not in my experience.
Strips cut through forested areas like this are generally called fire breaks. I don't know if there's a more specific term for those beneath power lines.
In Swedish it would be called "kraftledningsgata", directly translated to English that means "powerline street", but I already saw a better name for it in the comments "utility corridoor"
I haven't done the full length of one but I've gone pretty far down one before
Basically you just need to figure out who owns the land and depending on that would depend on if you can legally or not
When I did it though I didn't check first because I was basically banking on the fact it was near a national forest so if someone stopped me I'd claim (accurately) that I didn't know it wasn't a part of the national forest. Of course I'm not sure if it is a part of it or not, but if I did get stopped at least I'd know for sure. I didn't get stopped but I did have a nice day out there.
The area where there are always open camping sites in that one national park because no one wants to sleep under the high voltage lines and get cancer.
It may burn, but the gap is supposed to prevent the flames from leaping to the other side and burning that as well. It is moot if both sides catch fire independently
I see you're buying into the corporate propaganda. Guess who paid for "studies" to clear power companies from liability.
Here are a few of the conclusions from studies that have discovered a strong link between proximity to power lines and health problems:
Cancer: Exposure to power lines has been connected to cancer. Brain cancer is the most common type, but associations with breast cancer and leukemia have also been claimed;
Tumors: Some studies have shown associations between brain and other cancerous tumors and exposure to power lines.
Miscarriages;
Increased susceptibility to illnesses such as cancer;