It seems, as we suspected, that they fixed the boiler right before we went away for the weekend. Suddenly our too cold building is too hot.
Every dipshit in the building (including us, by which I mean me, when we got home) closed their radiator valves.
Because of the building and radiators are old, they filled up with water and began leaking.
They drained our radiator (traumatic and gross) and put a new steam regulator thing on it -- no more shooting water. They also said we had to leave all the radiator valves open so this doesn't happen again/elsewhere -- I just opened, those, cleaned up a few drips, briefly dealt with spraying water and all is fine now.
Then they went upstairs to do the same for the upstairs folk, which was the nasty stuff leaking into our place. After the ceiling dries out and they're sure everyone has gotten the memo, they'll patch the hole.
Now to just keep an eye for no more drips (although there seemed to be very little over the night and none when we got up.
I'm going to go to work now, then come home, put the furniture back and try to scrub the damn walls.
All in all, pretty minor, not even that big of a headache, but last night the world was ending (we also had a clogged toilet and tripped the circuit breakers, and one of ours is wonky, so I couldn't get it to go back on until this morning when I was calmer).
Sometimes the universe hates us, but that is perhaps just to prove to us that we are better than we think.
Jesus Fucking Christ.