(1) If the train stops only at San Francisco, San Jose, and Los Angeles, there will be no urban sprawl, because these areas are fully built out.
(2) But that's not the deal. The plan is for the train to stop at Gilroy, Merced, Fresno, Hanford, Bakersfield, and Palmdale. Each of these towns is to become a commuting center for local residents who want to work in the metropolitan employment centers on or near the coast. The HSRA boasts that the trains will carry 69,000 commuters per day.
(3) The housing built for these commuters will be sprawl housing because there is plenty of farm and range land to spread over, because the sprawl lobby wants to build this kind of housing, and because the planning commissions and governments are putty in the hands of the sprawl lobby.
(4) The sad thing is that it won't work, because when the line finally opens for business the commuters will find that the two-way fare, five days a week, is far more than they can afford, and so they won't ride it anyway. Even with $10 gas it will be cheaper to drive.