The solution is of course to get a communal system. As a bonus, drilling one giant loop is significantly cheaper than drilling hundreds of smaller ones.
It doesn't work this way. Dense cities just don't have enough space for geothermal heating. It really works for single-family homes only, or maybe just a slightly more dense areas.
Not to mention that city infrastructure is WAY too expensive to build, anywhere. You'll spend more money on planning than on doing the actual construction.
>The solution is of course to get a communal system.
If it's that simple why is Austria not doing this in the cities? I don't know any voter who opposes cleaner air and cheaper heating.