It has been spoken of for 30 years. I read the original book. Nothing groundbreaking , but fun to see videos of how they live.
The author mentioned that since then (he waited for 10~ years to release the footage), all of those holes/places/most of em, were occupied by new rail workers or sealed. I guess they don't like when people steal that energy. Probably they want to keep it for bitcoin or something. (smiles) This story is just a prime example that even with few square feet of personal space, a man can make a living or more. (he kept it quite clean) Few square feet, - a difference between fixing computers/printers & needles on a sidewalk of skidrow.