In reality, after MK closes and the transportation shuts down, the only way to get to BW is to either go to Epcot and walk through, but after Epcot closes at 9PM, not an option anymore. You can then take a bus from Poly to DTD and then transfer to the BW bus there, a VERY long way to get there. Your best bet is to take a taxi to/from any of the MK resorts if you don't have a car.