Here is yet another video from the Divergent set from FilmSpyESHG. This one is way closer. We can hear the Dauntless Initiates yelling as they run to catch the train. I’m guessing this is when they run out of the building where they picked which Factions to transfer to.
If you look closely you can see a stuntman/initiate climb to get to the train track.
All of this amazingness all in one day is truly incredible.