Rail Transit makes sense where there is an existing rail corridor. Outside of that, not sure it does. Last mile links might count. But those tend to grow, into their own corridors. Any end of line location needs a place to store vehicles (which is why Central bus depots are terrible). So a rail line call never naturally terminate in a CBD--it must pass through.
That said, for single line networks, the terminal station can store one train, and operate such that when a train on one track arrives, the train on the other track departs, so there is always a track available for an arriving train. Trax operated this way for years. Now days, UTA builds long tail track at termini to store trains. Which works at peripheral locations, but not for a CBD location.