It seems that originally, LU and the police had a plan to put on special train(s) from Hainault to Liverpool Street to bring the EDL to their demo. RMT reps objected, and told LU that it expected that members would refuse to work on safety grounds if hundreds of racist thugs came through their stations and onto their trains. LU management swiftly knocked the idea on the head, and the EDL itself admitted that the police told them that the initial plan had not taken account of the likelihood of RMT scuppering it. (Shortage of drivers on the Central Line may also have been a factor!) The union also got texts around advising members of their right to refuse to work on safety grounds.
However, although Kings Cross was closed for a short while for a 'fire alert' (that's what management called it, anyway), the EDL did eventually travel from Kings Cross to Moorgate with their police escort. And the EDL did manage to hold a small rally (less than 100 of them) at Liverpool Street. Perhaps they were able to do so because opponents thought they wouldn't be there due to widespread reports of workers preventing them assembling there?