You maybe interested to know the TfL were the first metro system to use this system, they actually developed most of the technology themselves, and now sell it to a number of other cities.
here’s another fun fact: TfL turned on contactless payments for all their stations without any apparent changes in their user facing hardware. one day the same oyster card reader started accepting contactless payments. i’m sure it was not as simple as turning on a switch but it looked that way :)
