In the past, there has been discussion about allowing mobile phone
operators to install base stations below ground and provide some
coverage for folks on trains. This is yet to happen?

I was on a tube train today and was thinking sod that...

What we really need is internet wireless hotspots on each train,
connected to the rest of the world via the train wheels? Could the use
of Power Line Technology (as done in the home with those plug-in mains
ethernet adaptors) help here?

Be far more useful to the travelling public than a mobile phone service
that enables Sharon to witter inanely about the minimun distance she
should dance from her handbag at the disco...

--
Adrian C