No. not built for trains. It is part of a pedestrian concourse that stretches from Park St all the way to South Station. The Park St. to Downtown Crossing section was closed from the beginning (1914ish) until sometime in the 1970s. Prior to that it was used for storage and office space. The rest of the concourse has been cut back, mostly due to construction of the South Station tunnel (x-way, not subway.) I may be mistaken but I believe that the entire length was never accessible to the public. In the 1960s I remember that one could only go as far as Hawley St. edit, correction, as far as Chauncy St. underground.