In the DVD commentaries, it's made clear that they don't film outside mainly for scheduling reasons. It was a pain in the ass and often threw the filming schedule off, so they stopped doing it unless absolutely needed.

Something was going on. Dan addressed it during Harmontown last night towards the beginning of the show.

That Deadline reported it is the reason that I'm giving it some weight. That reporter was among the first to say that it looked like Community's Season 5 was going to happen, and it did. And she was covering a majority of the network pickup news this week.

The MacGuffin Institute was the first thing that really threw me off in this episode. If it had been a name made up by Abed or Troy it would have worked fine, but in the past, Community was always somewhat grounded in the real world (except for within the Greendale campus or Abed's brain). It's very Airplane-like…

Or Steve Martin