Complex sentence: Danforth line and will eventually become the only train model to serve the line, the Sheppard line is currently the only subway line to be served exclusively with T-1 trains consisting of four-car train sets.
Split into simpler sentences: Danforth line and will become the only train model to serve the line. The Sheppard line is the only subway line to be operated exclusively with T-1 trains consisting of four-car train sets.