Each of the trains has a different character, with Bakerloo being a detective, Circle a hippy chick, Victoria a caring grandmother, Jubilee a gadget-mad teenager and Hammersmith and City competitive twins.There will also be visiting trains from the US, Russia and Australia. (Maybe the Australian one will be an Akubra-hatted roadtrain named Bruce or something.)
The press are having a field day with this, in light of ongoing commuter misery on the creaking system. Metro suggests some plot lines, involving characters fixing the dodgy brakes on Northern Line trains and rescuing fainting commuters in an episode named "Summer Fun" and a maintenance man using the wrong spanner to fix tracks. Meanwhile, the Times article on the series is quite sarcastic.