Snowpiercer is a helluva movie. Any ambiguities in the plot are resolved when one considers that the entire film is a metaphor for life and the struggles of the haves and the have nots. One revealing moment that mirrors the real world comes from the classroom where the children are being force fed political propaganda and then regurgitating it to the delight of the adults that reside in or near the front of the train.
The climax is superb when Curtis finally learns the awful truth about the train and that one of his closet companions (Gilliam) had apparently been conspiring with dictator Wilford all along. Another metaphor that mirrors the real world considering that governments and leaders all read from the same playbook regardless of national or political affiliation. Wilford expands on this when he reveals that all of the uprisings and revolutions were planned and coordinated from those in positions of power and authority (ie: government) on the train.
The ending leaves hope for the future when Yona learns that she was lied to and all life is not extinct after escaping what’s left of the train and witnessing a polar bear walking on a snowy ledge. Fantastic movie that I highly recommend.