It is _being_ rebuilt: the apartments building is done, but the surrounding areas are construction, I just didn't have the energy to walk around after a long day of those hills. :-)

I don't know what its official status is (or why do you believe it's not for tourists) but it is full with apartments to rent (under various names, some of them running separate businesses as we heard from other tourists; you can find a lot of those on bookingcom), and visibly it has been designed for that, since there is a touchless keycard system (PIN enter, codelockers, keycards) and a porter service at the entrance. The parking spaces are numbered and assigned to the apartments.

The customers are the tourists and there were plenty when I was there, and if you're right then also the owners ("private"), but I cannot sort them out one by one. IMO "customers" is the best way to show that if you aren't belong there (tourist or owner) you can't park there. The best if you go there and ask the porter, or the owner of the building.