Well, I have been investigating and in fact trains do stop in the stations, but is completely randomized. Is quite possible that in a beginning the developers planned a regular service as stipulated in the in-game schedules, but for some reason it broke at some point even during the developement and it was never fixed as the impact in gameplay is minimal. You can wait in a station a entire in game day and no trains can pass, but in another station another day up to 4 trains can pass trough the station in an interval of 1 in game hours, and the last train of those can stop at the station, cargo or passenger, does not matter.