I only saw the first season of the UK version. My friend, who has seen the UK version, actually told me the offices would merge, but he wasn't specific how they merged. He also told me (he's such a spoiler, isn't he?) that the boss in the UK version was fired or something, so I had assumed the merge was the other way. Of course, I was told all this several episodes into the current season... otherwise, I wouldn't have made my bet with my coworker with my false assumption. Sometimes, it's good to be wrong, I guess
