In Snowpiercer, Networked Communications are not mentioned outside of the phone system that Wilford installed, and the very start of the movie there are a stream of newsreels.
The news is depicting the end of the old world, and tells the story of the miracle global warming stopping device being deployed. There are panicked news anchors discussing how the device is malfunctioning and causing the world to freeze over and then no more.
The phones are only directly used once when Wilford makes Curtis listen to his friends being killed; however, Gilliam and Wilford used them offscreen to plan the population controlling rebellions. It is important to note that the phones are never used positively during the movie and are seen as a tool of Wilford’s oppression. The only communications allowed are directly to Wilford, and are a powerful tool for him. For the tail passengers all communication is done by word of mouth and this causes trouble when communications need to be made to other sections. For example, when they are attacked in the tunnel they have to shout from train section to train section in order to get the match to save them.