As a personal rule I stick to the 15 mph difference and stop splitting around 45-50 mph, but regularly see guys flying through at 30-40 mph difference. Things happen to quickly at those speeds to react in the little bit of space you have.
On the toll bridge thing, all the Bay Area bridges were originally sold to the public as being toll free once the construction costs were covered. Then when the scum(politicians) started raiding the gas taxes to cover their pet giveaway programs they came back and asked for a raise on the tolls from 40 cents to $1. This was sold as a final and permanent increase. He scum then figured out how to get around the supposed cap in the proposition that gave them the $1 toll. I trust a politician as far as I can toss one. If they find a political advantage in ending lane splitting they'll try it. One thing that prevents it is the police unions(including CHP) have a strong lobbying effort in Sacramento against outlawing it.