Aside from the practical difficulties of loading gauges etc there are other reasons it is not going to happen anytime soon.
Security, Immigration and Customs is carried out where? At each and every station that passengers get on and off? Most people do not live near a railway station and will still drive to the airports, therefore the load factors on routes will be low.
As for the claim that the Lockspeiser design was a brilliant concept, . . . . it appears the rest of the world were/are too thick to appreciate its brilliance!