Even though i don't care for it in a movie theatre, the FCC has traditionally taken a pretty dim view of trying to block someone's authorized radio communications.
Loads of buildings don't allow (or practically don't allow) cell signals :: nothing stops them from being built.
It's active interference the FCC takes a dim view to - passive interference (thick walls, loads of metal, etc) is fine.
There's a theater near me that I can get 4-5 bars of LTE outside, 1-2 bars near the doors, 3G just 20 feet inside, and only 1x or a bar of 3G in each screen room.
Don't see the FCC dropping the hammer on them because it's the way the building is constructed, not active interference
I think the idea is cool, but I have a feeling there would be quite a legal battle that ensues when someone is injured or dies in the hostel after they couldn't connect to 911.
Train tunnels, underground car parks and other reception black spots seem to have avoided litigation. Have we really reach the point where going outside to get reception is not something a reasonable person would think of?