I thought it was SWER (https://en.wikipedia.org/wiki/Single-wire_earth_return ) but in fact it's something closer to "radio current", as explained in this 20-year-old(!) article:

http://amasci.com/tesla/tmistk.html

The biggest problem I see with this is that it will cause a lot of radio interference --- a long wire with that much power going through it at the frequencies they use will basically act like an antenna.