Bus lanes in Paris are physically separated from car lanes, so that motorists are less tempted to cut into the bus lane, but if the street has only one car lane, the dividers are low enough so that emergency vehicles can cut across lanes to get ahead. Furthermore, the bus lanes are wide enough to let two-wheeled vehicles pass stopped buses. Two-wheeled vehicles are allowed in the bus lanes even though some roads have parallel bike lanes.
Human Transit has pictures and more.
As a comparison, some Singaporean drivers seem to think that 1) cyclists shouldn’t be in bus lanes, and 2) if a cyclist is in a bus lane during the bus lane hours, it’s OK for cars to violate traffic law, cut into the bus lane and pass the cyclist at a dangerous distance.