Everything knows what it releases and to what (I have a sinking feeling that they shouldn't....)
BikeContainer should know what its spare capacity is
BikeContainer should be able to stock up on randomly broken bikes
Van should be able to identify what it needs to release to a particular bike container
Van should be able to transfer as much as possible to a garage
Van should be able to transfer as much as possible to a station
Van should be able to complete a transfer with a garage
Van should be able to complete a transfer with a docking station