What bus system works out of the San Bruno Caltrain station?

Depends on where you're going. Samtrams 397/98? Stops next to it another heading toward redwood city and beyond stops in close proximity to it. For a wider selection of buses you need to walk a few blocks up past over pass to the mall/bart / bus area behind the garage and effectively a block past bart to bus stop for Samtrans buses. At least 3 maybe 4 bus lines link there

Down San bruno Avenue towards el camino