Historically, there have been cases where a single large steam-heat or hot water system served multiple buildings on a corporate or university campus, or even several ciy blocks (I think that was in New York). No reason you couldn't do the same with a heat pump.
I studied at Rensselaer Polytechnic in New York and they have a campus-wide steam system. There are tunnels below the ground connecting every building. It is somewhat common to see in that region.