I've been following the project for a year now and Clemens Elflein has actually managed to get the topic off the ground professionally. Recently, his kit is available, with which you can upgrade a cheap Yardforce robotic mower to GPS support. This eliminates the need to lay boundary wires.
As far as I have understood, the system just needs data from one rtk station within approximately 10 km to retain 1 cm precision. So if there already is one that close to your home with publicly available data, you might not need any rtk station at all