London busses arrive every 5 mins not every 30 mins. At high throughput bus stops busses arrive pretty back-to-back continuously. Trains arrive every 90secs not every 15mins, often the next train is waiting just outside the station for the previous train to depart.
There are over 500 different bus services in London managed by TfL. 11 Tube lines covering over 200 miles of track and 272 stations. 6 suburban rail lines covering over 100 miles of track and a 113 station.
TfL is a major operation, and its fare collection system is one of the most efficient and technically capable systems in the world. So good they sell it to other cities like New York. I can absolutely guarantee that the cost of TfL fare collection system will be an insignificant fraction of the £2.2 billion that TfL collects annually.
(This one time I was at a party (it was a long time ago) and these Italian dudes were there, and when I mentioned that I was from SF one of them said, "Nice town." ... I was a little miffed, but they were from Rome, so... *shrug* )
Given the license tracking already going on for bridge tolls the infrastructure may already be there.