Probably worth double checking as it seemed too good to be true. I used the Stagecoach journey planner, but I have no idea how reliable it is for public holidays. https://www.stagecoachbus.com/plan-a-journey
That link for some reason doesn't mention the shuttle bus service from Brighton station which will obviously be of interest to a lot of people. I checked the programme from yesterday and it is listed there.
These are the extra transport provisions the club are having to put in place for Boxing day and no doubt having to pay very handsomely for:
Shuttle Service from Lewes Station.
Shuttle Service from Brighton Station.
Brighton University Lower Car Park.
Sussex University Multi Story Car Park...
Yes, it's definitely Southern who have the upper hand, not the club. If there was a breakdown in the relationship between the two then they could refuse to call at Falmer on match days.
The franchise (or more accurately a management contract) runs until 2021. There should be a DfT consultation...