Re: Should have been designed into or alongside GSM-R
GSM-R was/is only made by two suppliers - Siemens and Ericsson. the rest quite rightly concluded it was commercially non-viable and a waste of development time.
To be fair, Railtrack did ask the UK operators to quote for it to be installed on WCML but they all declined as the cost was too high and Railtrack only wanted to pay 'on use' and as the operators could generate more revenues on Oxford Street in a day that the WCML would generate in a year, it was a complete non-starter. I know this as I was there.
The main reason why its a problem is the nice, metal laminated windows on the trains and the lack of available inter-carriage connections. You might stick an aerial on one carriage but you cannot route RF through the carriages on the inside very easily, so you're stuck with putting aerials on the top of the train right next to the second biggest source of RF interference where the power lines run parallel with the train.
And as GSM-R is a safety critical system, theres no way anyone on the safety side is going to allow the two infrastructures to join up.
GSM-R was certainly only built for 3G at best on WCML as the good old whining public didnt want to pay for Railtrack to straighten out the curves and lift the track to ground level to speed up journeys and as a result make it better RF coverage from existing towers.