Certain routes - even the local SAA - Watford branch had plug points and a portable phone set was carried on units , such that it was possible (if you knew where the plug points were , which was a stub off the track route internal telecom route was, often at stations) , hopefully plug in and ring an internal number on the railway system)
Before the public had access - the first generation "mobile phones" - with a battery about the size of a jerry can were issued to the largely class 50 hauled trains from Exeter to Waterloo (phones handed over at Salisbury to the station staff for the next down train) , as in case of failure , out in the deep country , it could be a very long walk to any kind of signal telephone or landline. Around 198x - a good idea.
I found the North London railway equivalent in a store room at Watford and asked if the Science Museum would like it , alas they already had a few. Went to the tip.