Board Thread:Spoilers/@comment-25176701-20151210024220/@comment-25176701-20151210203812

The group of Grounders we see towards the beginning are the Ice Nation. You can tell b/c they are carrying the IN flags (the ones with the blue handprint/spiral).

Also, taking a second look, I do agree that the doors were opening to the outside of Mount Weather, and yeah, JR said the transport vehicles belong to MW, too.