EWS on the Dash: Controlled by the BMS. Hence, lack of 'EWS Ok' signal from BMS.
No neutral: The gearposition is transmitted by a pot.meter to the BMS. If no power to BMS, no neutral signal to display.
Dip Beam comes on, even no start: No engine-off signal from BMS, i.e no command to ZFE to not turn the light on.
The dip-beam on may perhaps not make sense, but look upon it this way: You drive along at night, with ligts on, and all of a sudden, the BMS fails to communicate with the ZFE. If the system was wired in such a way that the ZFE would need a positive "Engine Running" signal from BMS to leave the lights on, then a BMS failure would leave you in the dark. On the other hand, if you design it in such a way the the lights stay on unless the ZFE receives a positive "Engine OFF" command in order to turn the lights off, a BMS issue, even if it will shut down the engine, will at least allow you to keep the lights on until you safely can turn the bike to the side of the road on stop.
So you see, it's all conneced, in it all makes sense, eventually
Good luck with your search