In Denmark the government have allowed people who live along some of the largest underground powerlines to install geothermal equipment to heat their houses.
Anyway, this is very different.
In an electric wire part of the energy is always transformed into heat and wasted, so it's nice is someone can use it.
In this device, they add something to absorb part of the energy that otherwise would have traveled to your neighbor, so the transition tower must increase (slightly) the energy used.
It's like digging a hole and replacing a part of the high voltage cable with a device that makes more heat on purpose to heat your home.