Interesting post, that raise points about a number of issues. While, from the point of view of overall marketing and service co-ordination, the Liverpool-Norwich should be an XC service, should it actually matter who provides the service. The problem arises when a current provider of a service that extends outside its natural remit decides that it is unprofitable, or of lower priority than its native services, and so downgrades it.
Is there any scope for flexibility in driver provision between TOCs? If a long-distance service is provided using stock that is common to all the TOCs whose boundaries it crosses, does it have to use staff from only one TOC? If there were a demand for a non-express cross-country service from Swansea to Scarborough, why should it only be driven by, say, TPE drivers?
And then, what is the balance between DfT planning and commercial opportunity? If a provider thinks of the service that they are only doing it because the DfT instructs, there might well be a tendency to downgrade that service. Perhaps more reason to give the service to its "natural" TOC. Every service (even one at 05:00) is a commercial opportunity and should be handled as such.
Finally, while I appreciate the point about different types of productivity, is there not some scope for running otherwise ECS as public services, or is the extra cost too great?
Many of the questions you raise should perhaps be answered by someone with more knowledge of commercial and marketing matters.
Just a couple of points though, not directed at you I hasten to add.....
Why do some people think that the Liverpool - Norwich route is not naturally in EMT's remit? I don't remember seeing anything official that states that EMT should work London and Local services only?
I can see how it would fall within XC's "usual remit" but then again so could most TPE services.
I also don't hear many people complaining about XC running the Birmingham - Nottingham services despite them falling more naturally within EMT or London Midland's line of work?
What would happen if XC took over the Liv-Nor route then? I would imagine the same 158's would be repainted into Burgundy/Silver, the traincrew's would have a new uniform, and fares would probably rise a lot seeing as XC crews are on a much bigger whack than EMT's. I can't think of any actual service improvements for the passenger!
To get back to Oswyntails question of traincrew's working other TOC's services or stock, it does and has happened, but is normally only a short term or occasional occurrence in my experience. Us Central lads used to work MML 170's to Coventry with an MML Steward(ess) on the trolley. I believe Anglia crews also work EMT 158's to Yarmouth? We also had a couple of Anglia 170's for a week or two in Central days. More recently SWT 158's appeared on EMT services.
It could happen more, but there is a lot of politics and red tape and other bumph between Management, TOC's and Unions to negotiate. Training/Briefing may also be necessary as one TOC's units may have subtle differences to another TOC's units, even if they are of the same class. I remember the first time a Central Driver jumped on an MML 170 on one of the aforementioned Coventry's..... He nearly missed Loughborough as no one realised that the brakes were adjusted differently to the Central 170's.
I agree about the ECS movements though. I see no reason myself why a scheduled daily ECS move with full crew on board should not operate as a passenger service, albeit with an anomalous stopping pattern if routed via diversionary routes. I suppose some movements across the country may have to be turned onto permissive Goods lines for operational reasons. This would negate their use as passenger trains. There may be other reasons too.