The proposed idea primarily addresses mobility as an experience. The idea is to connect the train track at Greenfield Village with the adjacent train track just outside Greenfield Village that runs directly to the Michigan Central Station. Once connected, the Greenfield Village train can pick up passengers at the Michigan Central Station and provide the "lost in time" experience of an old fashion train picking one up from an old fashion train station. It would be an exciting experience that would draw locals and tourists from all over.
Aside from the entertainment draw, there is also practical utility from having a rail connection from Corktown to Dearborn. For instance, since parking will likely be an issue in Corktown as the population increases with the new Michigan Central Station Ford Campus development, commuters/Ford Employees can park at the Greenfield Village and hop on the train to work at the Michigan Central Station. I for one think that would be awesome!