As you did not cite phrases from your references, I checked the content but found not relevant information, unfortunately:
The 1st link is a QA report about the rail industry:
Quality assurance report investigating the administrative data sources used in the production of short-term economic output indicators.
:
Despite the issues highlighted, the data NAES use from ORR has the most comprehensive coverage of the rail industry available, covering more than 99% of passenger rail movements.
https://www.ons.gov.uk/economy/economicoutputandproductivity...The 2nd link studies the mobile network, not the rail network:
Providing reliable mobile network on trains is a challenge. … In order to develop a comprehensive view on the subject, this short, desk-based research study was required to …
https://www.ofcom.org.uk/__data/assets/pdf_file/0018/50085/r...Conclusion: Neither study relates to the subject of the question: « desserte la plus fine du territoire » and cannot used for support.