and once again, it depends on how the alternative is deployed. the majority of people in the the Brighton and Hove, and wider catchment area, are going to travel in via Brighton Station and 100% will have mobile phones. if tickets are available on the day at the shop, at the station or by texting to charge up some smart card, it will work out just fine.
No, 20% of he crowd max will be able to travel by train.