Most rail investment in the UK is ultimately paid for by the government. E.g HS2, line upgrades etc. Train companies might make a contribution to the cost of buying new trains through the cost of leasing them from the government regulated monopoly companies that buy them with government money. We basically have a system where everything is paid for by government but in a really complicated way involving lots of complicated contracts written by very expensive lawyers. Our trains are now some of the slowest most expensive and most uncomfortable in Europe.