Re post #4354 Tanker46.
Hello Alexander, the 4th rail track belongs to London Transport. Its all down to the complicated history of the former railway companies.
My route is a representation of the Metropolitan Railway and the Great Central Railway. Please see attached link that explains it in detail viz loco changes.
The LM region did have until fairly recently the 4th rail means of electrification on it's routes from London Euston and London Broad Street (now closed) to Watford Junction, Croxley Green (LMS and now closed) also to Rickmansworth Church Street (now closed) . London Broad Street to Richmond also, sharing the tracks with LTE from Gunnersbury to Richmond. From Queens Park to Watford Junction the Bakerloo Line shared the tracks. Due to modernisation most track is now third rail or overhead and if any 4th rail track is left that would be down to running rights with London Transport now known as TFL.
It gets complicated the further one goes back in the railway history of London.
https://www.railwayarchive.org.uk/all-change-at-rickmansworth.
Cheers, Ken