Today's was at 8.34am on the Central Line train at St Paul's Station and staff stayed with the woman until an ambulance arrived to take the mother-to-be to hospital. The train was delayed by about 20 minutes, so I imagine there would have been much tutting from the City workers for the inconvenience.
There was an 84 year gap between the last two babies born in a Tube station. Marie Cordery (supposed called Thelma Ursula Beatrice Eleanor) was born at Elephant and Castle station in 1924. Then in December 2008 a baby girl was born at Kingsbury Tube station.
That's not really a lot of Tube births considering the number of pregnant women that must travel on the London Underground each day. So maybe that's why any birth or near birth hits the news.
Plus the press are probably itching for the child to be called Theydon Bois or Beckton or some other Tubey name. Maybe the current one will be called Paul or Paula!