I'm sorry, but that is a weak excuse. It is not necessary to have everybody sitting in one big open room, in an environment where anybody can interrupt anybody (or everybody) at the drop of a hat, to be agile.
I would also argue that if your project is being that reactive that it should be considered an anti-pattern, and that you should examine ways to make things less chaotic (erm, I mean, "agile").
Just because anyone can interrupt doesn't mean this happens all the time. People are pretty considerate, and if you need to concentrate you'll be left alone.
As for 'anti-pattern' I'd say that describes our set up rather well. And yes, changes need to be made to make the work more predictable but until someone cracks that nut the boots on the ground definitely benefit from sitting together and being able to turn to talk.
There's a machine to help you be left alone. It's called a door. They are outstanding, if you have one.
People initiate communications for social reasons, or if they cannot proceed on a task without additional information. These "choke points" don't line up, from person to person. When you're at a choke point you have a decision to make -- defer work and interrupt your own flow, or interrupt the flow of someone else so you can keep your own rolling.
Unless problems are pedestrian or communication times are aligned, it's zero-sum. And that's presuming that the initiator has kept his own flow going (at the expense of someone else's).
You can sometimes (but not always) maintain a queue of tasks and switch to another, instead of interrupting someone else.
But the best thing to do is to get into flow prepared. Figure out beforehand what you don't know, and get it straight. Don't just dive in. Spend a few minutes sorting out what you're missing, line that up first, then head into flow.
I would also argue that if your project is being that reactive that it should be considered an anti-pattern, and that you should examine ways to make things less chaotic (erm, I mean, "agile").