I don't know if you could call it automatic, but it's very unlikely your husband will slip through the cracks.
Although vehicle theft isn't a violent felony, it is a crime of moral turpitude, or dishonesty, so he will be subject to deportation, exclusion from reentering the US in the future, and denial of citizenship. There is a "petty offense" exception, but that requires a sentence of 365 days or less. Since he was sentenced to state prison, and prison sentences are at least a year, that won't help.
Did your husband have a hold in the Shasta County Jail? If so, The California Department of Corrections (CDCR -- they added "Rehabilitation" to the name a few years ago, but they still focus on punishment) will be notified when he is transferred to a state prison facility.
If ICE (Immigration and Customs Enforcement, the new name for Immigration and Naturalization Service) has not yet placed a hold on him, it probably will at some point during his incarceration. CDCR will also run checks on him as his release date approaches, and will notify ICE before his release to they have the opportunity to place a hold on him if they haven't already.
I'd suggest you contact an immigration attorney. You can also find information on line at
www.ilrc.org, the Immigrant Law Resource Center.
One last thought: Did your husband plead guilty or no contest, or was he convicted after a trial? The court was obligated to advise him of the immigration consequences of his plea. Usually that is in a written plea form the defendant signs, and the judge also does it verbally. Failure to advise a defendant is grounds to set aside the plea.
Bob Marshall
Chico, California