Hi, I'm sorry for the late reply, I didn't really see this topic before earlier today,
BUT as it is I do have an apartment in Olso, or rather a.. hole-in-the-wall, hehe.
It's not much, but I'm pretty sure it could accomodate four people, that is, if you're not afraid of slightly intimate sleeping accomodations.
I have one sleeper sofa 140cm wide, and a "hems," which is a bed built out from the wall, 120cm wide, in which you could pair up.
As mentioned, it's a small place, but it might just beat sleeping in a tent, at least considering this weekend's weather forecast.
So, if your plans are not yet set in stone, and you are not particulary claustrophobic, my hospitality is yours.
Should you be interested, you could reach me here or at FA for more details.