Its probably all part of antisocial behaviour legislation, from the government that gave you ASBO's you can now get a criminal record for putting your feet on the seat. The fixed penalty has to be enforced by the magistrate, they can't be judge, jury and executioner.
Does that not make anyone else want to go on one of them trains and do something bad? Like wipe your naked arse over a seat since it doesn't say you can't?! Fair enough if she had dirt on her shoes or if someone else was wanting to sit down either warn her or fine her. But a criminal conviction? Ludicrous (sp).