Visited on May 7 and charged with eCarUp, no issue.
Signage was added! It now says access is only for the visitors of the houses and offices around, max 6h and is paid. The tariffs aren't posted, but by using ParkingPay it seems to be 1CHF/h.
No idea if just coming to charge is also a justification for parking here.
There are still no parking spaces designated as charging spaces.
When trying to stop the charge from the charger screen, it asks you to type a code. I have no idea whether "Please enter 0000" is supposed to be a placeholder, but if you literally type 0000 then the charge stops. This is the most useless protection ever. And there's already an "Are you sure?" confirmation step, so it's a 7-press operation to stop the charge.