I’ve had a quick look through the book. It seems quite good at describing the process of design within an organisation such as BR. It’s worth noting that, in 1946, when BR was formed it would have been one of the biggest organisations in the UK.
I don’t think nationalisation would have been possible before WW2, The scale of operations would have been too big for the available IT. The Big Four regional groups of railways were effectively a quarter of the size of BR.