Sure. As I said, I have no insight, it is the latter exchange, which I am interested in. It is shorthand, but presumably for the retailer (the operator in this instance) the cost of Delay Repay to the business creates the imperative to recover attributable costs from those suppliers you mention.
Up to a point, yes. And there are plenty of other costs associated with delay that an operator will have to be concerned with, including overtime and payments to Network Rail; Delay Repay is not necessarily the biggest ticket item.
However, the contracts supoorting the system may well not go down to that level of precise attribution. It’s common in the IT world for a service failure to be subject to an automatic payment mechanism related to the price of the service, not the consequences of failure - and with a level of acceptance in that mechanism that perfect performance isn’t guaranteed.
There can then be root cause analysis techniques to assess the actual reason for a failure, but these are generally not focused on money but avoiding recurrence - especially importantly if there’s a boundary between two suppliers.