This from the Office for Budget Responsibility - Economic and fiscal outlook, Box 4.2, page 98...
the classification of Network Rail:
Network Rail is currently classified as a private sector body. The ONS is reviewing that classification against the revised guidance in ESA10. Network Rail had £30 billion of debt recorded in its latest accounts, up from £8 billion at formation in 2002. Based on published plans, its operations imply the equivalent of around £3 billion of borrowing a year on average over the coming years. A change of classification could therefore increase PSND by about 2 per cent of GDP and PSNB by 0.2 per cent of GDP on average, with implications for future debt;
No doubt both TfL and Scotland are looking forward to managing, maintaining and upgrading their devolved railway assets?
