There are 34 pending MBTA capital projects to keep the existing system running, totaling a staggering $4.5 billion, which should beat out South Coast Rail, according to Paul Regan, executive director of the MBTA Advisory Board. These include replacing the middle-aged Red and Orange Line cars in the MBTA subway system. Another big-ticket expansion project, the nearly $1 billion Green Line extension to Somerville and West Medford, is mandated under the Central Artery mitigation agreement. The T doesn’t currently have the money to pursue any of these. Nor is it clear how the T could afford the estimated $14 to $15 million in net annual operating costs of a new South Coast Rail line once it is completed.