Not on a normal schedule, I walked down Mission today and stumbled across the new "Truck Stop Mission and 1st food alley."
They've managed to pull three trucks into this tiny alley that connects Mission with the courtyard of 50 Fremont. The trucks will be there Monday-Friday, 11-2, with different trucks on different days (website and schedule here: http://www.truckstopsf.com/calendar/2... ). The guy at the Pacific Puffs (cream puffs) truck said there would be two meal trucks and one dessert truck there every day.
I already had plans for lunch but I bought a cream puff which was pretty good: the pastry was tender but not soggy, even though it had been refrigerated (I let it warm up for a few minutes), but I thought the chocolate on top and the filling were a little too sweet (I would have liked a more sophisticated chocolate flavor).