My building looked into it (a complex of several buildings sharing one giant underground carpark). Installing 300 chargers (one at each spot) would cost millions and take years to radar and cut the channels in the concrete. Even if done, the city connection to the facility would need a million-dollar upgrade too going all the way to the local substation. And then the local fire department had an opinion: they were not happy at the concept of 300 EVs in one underground structure. There are no rules limiting such things today (also on car ferries) but we are one bad fire away from some firecode regulation about EVs underground.