Cornell did a study of open plan awhile back that you should all read. I posted it here: https://news.ycombinator.com/item?id=7507404
The misunderstanding here is that it's just about serendipitously "overhearing" other conversations.
1. Open plan makes it easier to ask questions. Those are "disruptions", yes, but what the Cornell study found is that in open plan it's actually easier to "read" a person and see if it's an ok time to ask a question, and to quickly reply or say ask me later, and so forth, to efficiently manage those disruptions. Compare that to offices where you are much less likely to ask questions, knock on a door, etc., and where when it does happen it may turn into a much longer disruption.
2. They found it also gives us more courage to ask potentially "silly" questions. Which can be the genesis of good ideas and help us get unstuck, contributing to team creativity and productivity.
3. They noted that developer reactions to office plans are often biased towards maximizing personal productivity in order to maximize (short-term) personal benefit, whereas the company benefits from a balance of personal and team productivity. That's a fancy way of saying we'd rather spend our time coding than helping others, so we may not instinctively appreciate the benefits of open plan as much. Which I think is the case here.