On 22/02/2019 17:30, Graham Harrison wrote:
The data feed to systems like RTT was (I believe) forced on Network
Rail. Did the same thing happen to LT? I can accept that with the
frequency of trains on the underground an RTT look alike is probably
not required but I'm just intrigued to know if the legal basis for
building it exists.

TfL have extensive public data feeds for all modes of transport they
cover. This is a good place to start:
https://blog.tfl.gov.uk/