When we are in a free lane, passing a line of cars that is waiting and idling, we have to anticipate that somewhere along the line a car is going to either suddenly pull out of the line right in front of us to pass ahead or a car will cross the idling line through a gap and cross in front of us. Neither car is likely to see a bike coming along, as their vision will be partially blocked until they are actually half out in your lane. They are looking for buses or trucks or other cars. They may well not see a bike- you are in a blind spot.
It's up to us to anticipate this because this traffic situation comes up regularly- it is not a freak occurance. When passing a line of idling cars we have to go slow and be ready to veer or brake suddenly at a moment's notice. Maybe not the first time or the fifth time, but sooner or later a car WILL unexpectedly pull out through that line right in front of us as we are happily zooming along.