There is a San Francisco Chronicle article which answers your point: http://www.sfchronicle.com/bayarea/article/BART-extension-to-San-Jose-on-track-but-new-cars

There is a San Francisco Chronicle article which answers your point: http://www.sfchronicle.com/bayarea/article/BART-extension-to-San-Jose-on-track-but-new-cars-11047689.php http://www.sfchronicle.com/bayarea/article/BART-extension-to... tl;dr: They need 30-40 more cars. Testing on 10 new ones has found issues (which is the point of testing). Contract says 25 more should arrive by the end of 2017.