That’s exactly why the ROSCOs came into being. Furthermore, because government TOCs are just cash flow entities, you need to avoid large changes in day to day costs and maintaining traction and rolling stock is potentially a very “lumpy” cost line.
As someone who had traction and rolling stock in his books of account in BR days (I was an Area Finance Manager in the M&EE function, later a Production FM in a sub sector), I am really glad I am not having to pay for the chaos that is the IET contract and all those emerging liabilities. I had class 50 locos, that was bad enough to budget for!
Funding rolling stock, as I have stated before, is not always done cheapest via the state financial arrangements. BR didn’t get its stock at nil interest and my predecessors often complained about not being allowed to seek external finance and having to pay inflated Treasury rates. That wasn’t only a rail issue, most nationalised industries suffered.
Repeating an earlier post, I have looked at the 2022 accounts for the big three ROSCOs and I can’t see where the ORR get their increased profits from. I can see and understand the dividends but those P&L changes from 2021 - I have no idea how the ORR got to those figures. I may ask them to clarify because they look very odd.