BART in the Bay Area is also a two-track system, and we face the same problems. This is the reason given (here in CA) for not running 24 hours, and the limited

BART in the Bay Area is also a two-track system, and we face the same problems. This is the reason given (here in CA) for not running 24 hours, and the limited window for maintenance slows down all track work. It also prevents anything like an express train from being possible. This might not work anyway given the relative distances and train frequency, but I would absolutely build my schedule around an express if such a thing existed here.