The way they've designed it the government doesn't have a choice. The entire transport strategy is based on a majority of the crowd catching the train, and if people had to buy tickets for it then the whole place would be chaotic. Imagine 40,000 people trying to scan in straight after a game. People would just go f**k it and the government gets no revenue at all. It's not like you can have ticket inspectors on a packed train.
Are all events held there forced to pay for free travel?