The modder keanuWheeze has added a working subway system to Cyberpunk 2077.
This mod allows players to use an overhead subway to quickly travel to different locations in the game. You can also look outside during the ride to view Night City.
While fast travel is in the game, the modder has incorporated the subway system into the game to make the idea of fast travel from point A to B more realistic. The Metro City mod is available here. In the gif below you can see what it looks like to travel by metro.
Cyberpunk 2077 is available for PC, PlayStation 4, Xbox One and Google Stadia. In the course of 2022, an upgrade should be released for PlayStation 5 and Xbox Series X and S.