Joey you've managed to ignore the entirity of that piece to focus on the end of it, which even then doesn't say what you think it means.
You could absolutely renationalize the railways by bringing the franchises back in-house as they expire (or as the private firms give them up) -
which is what McDonnell wants to do. What EU rules would require the state to do is to allow private firms fair access to the network, which they would have (indeed they'd probably have better access to it than now because the moderation of competition clauses that are written into most of the contracts would not exist) - McDonnell (or Corbyn) never said that they wouldn't.