Well, there is this cool physics/art installation of 1301 fluorescent tubes being lit by high-voltage lines [0].
There is the story I heard about early in the history of long-distance high-tension lines someone building an inductive coil to harvest electricity, and getting convicted of theft, which seem legit, since it is coupling with the lines and pulling more power than the grasses & ground would pull. There are also various references available online to cases, but the readily available ones don't seem to link to any court case (e.g., [1]).
I saw some back-of-the-envelope calculations about it being on the scale of 25 millivolts/mile, so you'd need quite a coil to get anything more useful than powering a bulb. Anyone with better calculations or actual measurements?
[0] https://jimonlight.com/2009/03/01/field-by-richard-box/
[1] https://skeptics.stackexchange.com/questions/23799/has-anyon...