If it were an interlocutor of the Scots courts on a piece of UK legislation then it would as a minimum be ‘persuasive’ for courts in England also. If it was a Court of Session cause then it would be ‘highly persuasive’.
Absolutely!
Going back to the thread topic, I've searched case law databases, I've trawled through Railways legislation back to the Victorian times, I've read closure consultation processes on the ORR website, and we have numerous examples listed in this thread of services that are closed without a replacement, or are put on a Parliamentary services, and all sorts in between.
SO my view is that answer the question "what actually happens in Parliamentary services aren't run" is ... nothing!
Whoever has written the legislation that is in force
today as opposed to Victorian times (mainly the 1993 Act and the 2000 Act) has clearly not considered that a railway undertaking in receipt of public subsidy and reliant on patronage from the Department for Transport would try to chance their arm and not run a service if required to. So they simply haven't included any expressly set out provision to cover for it. The authors of the legislation trust that the government will run any services they are required to run and trust that the government will make sure any private operators run any services the private operators are required to run. And that's it.
Now if the DfT started ignoring the law and allowing services to close without following the closure procedure
AND if a pressure group came along who were sufficiently interested to do something about it took the DfT or the defaulting operators to court, then the Powers That Be may choose to update the legislation and set out the consequences more clearly (as the government would much rather have a written procedure any day of the week than leaving it for a High Court Judge to decide what to do!). But even then, it's going to be a one-off situation if it ever were to happen. And in English law (I don't know about Scots law), there is no concept of compensation for government breach.
[This is something that does exist in EU law and in US Federal jurisdiction, so if the State of California ignores the Feds, a Federal Court can order the state to pay out cash to people affected, and likewise if a member state of the EU doesn't properly follow EU law, anybody affected can sue the country concerned for what they call "Francovich" damages.]
So the most likely outcome is an order of the High Court to the Secretary of State for Transport saying "you have 28 / 56 / however-many days to make efforts to run a train service between x and y again, or go through the closure procedure properly". But no compo would be payable and so it's not really going to cause the government to lose that much sleep. And I'd bet a fair whack that miraculously, just before the service was re-instated, they'd find some mysterious "safety issue" at a critical switch or signal or bridge, meaning it has to be a bus substitution.
In conclusion, to mis-quote Depeche Mode, it's a question of trust. We just trust and expect the relevant people follow their legal obligations.