I used the term “physical segregation” only metaphorically. Whether the two offices are in the same building or not isn’t the point. Staff are colleagues and often friends. They socialize and they may even talk about their work in settings outside their offices. An analogy is with Wall Street trading. There’re strict laws governing those who trade for proprietary accounts and those who trade for clients or “making a market”, but information do sometimes leak from one to the other, perhaps because of an overheard conversation, or perhaps worse.