Do you have data to back up your barbed retorts, or are you just treating your personal opinions as facts? I made an FoI request to NR concerning this, and they told me that they did not hold information on bustitution frequency comparing different main lines, and it would be too expensive to compule it. What is your source?
Why does he need a source? He's pointing out a fairly basic fact.
There is something like 20 miles of quadruple track out of London on the GEML, to Shenfield. There are no practical alternative routes to Chelmsford, Colchester or Ipswich and the Norwich alternative means an almost total diversion and a diesel drag, with the only common bits of track being at the two ends of the route.
The ECML, MML, WCML, GWMLand SWML all have quite a few more miles of quadruple track in place beyond London, which means it is a lot easier to keep trains running on one pair of tracks, while the engineers take over on the other pair.
South of the Thames, the warfare between the old South Eastern Railway, London, Brighton & South Coast and the South Eastern & Chatham resulted in multiple ways to get to various places, so diverting trains or directing passengers to trains using an alternative route are all easy options.
The Chiltern Line is about the only other route out of London where double track dominates close into London and even there, they have the option of routing trains via Aylesbury if the line south of Princes Risborough is shut (done last Saturday when the main line signals failed in the morning and often done during programmed engineering work), or from the northern end of the route running to Oxford or Didcot to connect with GWR services/directing passengers to use Virgin West Coast. If Marylebone is shut, they can, for the time being pending HS2 work, divert into Paddington at the London end. I think they have yet to divert via Oxford to/from Banbury in the case of the Bicester-Aynho line being blocked, but so long as reversals at Oxford didn't mess up other services, see no reason why that could not happen either.
And LTS route services can divert to Liverpool Street or Southend passengers get directed to Victoria if Central is out of action, etc.
The alternative options for the GEML are almost non-existent, so more bus substitutions are the inevitable result when essential engineering work is taking place.
I don't need to make an FoI request to understand all that. I expect DarloRich would say the same