As far as I'm aware for a shield bubble to effect a different entity it must be docked to the entity with the shield bubble. If its undocked then they are separate entities and the shield bubbles will not effect each other.
Not sure what would happen if a ship docked to a station is in an adjoining sector to the station. It might be buggy due to crossing a sector boundary.
So a ship docked to a station inside a shield bubble on the station will be protected within the radius of the station shield bubble. The shield bubbles on the ship will still protect the ship as well, as long as the station has enough power to run it as well. But the ships shield bubble overlapping with the station won't protect the station. The shields only protect down the docking chain not up.