I’m not sure what you’re asking here, but I’ll add some info that may help you in clarifying your question.
You’re asking about a writ of mandamus, or as I understand it is called in California, a writ of mandate. See the Wikipedia entry here, but understand that generally speaking, a writ of mandamus orders a governmental body to do something within its jurisdiction: for example, in the case of the DMV, to reinstate a driver’s license.
More directly to the point of your question, I’d guess that the California petitioner could apply for a writ of mandate to reinstate his or her license after any suspension was over, but before receiving word that it was officially over–in other words, if the California DMV forgot to officially reinstate the license after the suspension period, the license-holder could apply for a writ of mandate to force the DMV to end the suspension and officially notify the license-holder.
I doubt very much that a writ of mandate could overcome a lawfully-imposed suspension, but I see no reason why it could not be used to reinstate a license if the DMV neglected to after the suspension is over.
Just some thoughts and guesses, anyway. I’d be interested in hearing from any California legal Dopers on the question.