Firefighters are incredibly busy. There is no need to stage something like this, it happens all the time. Probably got got called out earlier in the game too. Also, they are honest people generally. I don't see them staging this to this extent. That's a lot of firefighters pulling one over on their citizens. Plus the camera is rolling. Nobody is going to loaf around when someone's house is potentially burning down with people inside it.

Sometimes cameras capture cool things in real life. Enjoy it.