Yes, the wye has been there for years. Notice that it's a bit strange. There are 2 tracks on 11th and a car outbound on Market goes to the track that was the inbound track for the Potrero line while a car inbound on Market would go to the outbound track. Then there is a crossover on 11th that lets the car get to the other track. In the past (in the pre BART PCC days) quite a few cars would turn back at 11th, but it's a slow process in that the poles need to be reversed before backing out of 11th and then reversed again while the car is blocking traffic on Market. The track pattern allows several cars to be staged, something that wouldn't be possible with a standard wye.