That's why I like open plan in small spaces -- IE, a conference room with 4-8 desks in it for a single agile team. All business-related conversations probably apply to all or most of the team anyway, and at least for a development team the phone chatter will probably be minimal. The walls keep you from distracting unrelated employees with your discussions, but the openness keeps the highly-relevant people in the loop.
I have yet to see or work at a company organized like this. Usually it's dozens of people from multiple teams commingled in a single large room. Where I work now the entire company only has 8 people, but we have 5 different projects going on, of which I am only involved in 2.
