The January 1991 issue of Trains had an article about SP’s Lompoc and White Hills branch, which connects to the SP (now UP) coast line at Surf. While this standard gauge branch to White Hills is still in service, I have not heard anything about the 3’ gauge mining railroad at the end of the branch at White Hills.
It is not Manville anymore. An article in the Santa Maria Times from April 13, 2008 says that the railroad was operating, but it also talks about a modernization. Unfortunately, I cannot find part two, so I do not know if it is still operating after the modernization.