The bike rules in CA, with a few minor special details, basically say that bicyclists have the same rules and responsibilities as car drivers. So a Stop sign means Stop. Responsible bike riders (probably not wearing team jerseys, riding in a pack, and using $10-20K bicycles) usually slow down for Stop signs to the point where if somebody else is there they can completely stop. If nobody's there, they will probably slide through at a low speed then pull away - just like drivers doing "California Stops."

Where it gets interesting, if a cop is around, is the definition of "Stop" which is not abundantly clear in their minds if not in the VC. Many interpret it as having put a foot down, but it's very possible for a bicyclist to stop fully without placing a foot on the ground. The VC doesn't require the foot down - it just requires that motion be stopped. A smart bicyclist is moving slowly enough approaching the Stop and looking around enough to notice the waiting cop and put the foot down, rather than do a rolling stop or a track stand.

The TGV thing above was an organized bicycle race, not a pickup bunch terrorizing local roads. The organizers blew it regarding route choice and coordination. The police and road people may have wanted them on the side road (not thinking about the grade crossing) rather than closing a more important road (with a grade separation) - but that doesn't excuse either lack of coordination by the organizers or stupidity of the riders. The ones in back who got held up probably did lose any potential for placing in the race - but they were far enough back that they really were just "along for the ride" anyway.