Might not scale well if it heats up the localized conduction region or leaches out. The NYC subway use to need to be heated quite a bit because all the surrounding rock absorbed all the heat. Now, it’s saturated and requires massive cooling systems
“Why it’s (almost) impossible to cool the tube” https://youtu.be/hQo6_GkITe0
Quite informative.
At least with above ground water probably easier to dispel the heat .
They also have issues in desalination plants of pumping the resulting salty brine back.