In terms of the likelihood of future similar operations, what I see are these major factors:
1: The suitability/reliability of the rolling stock. Clearly these new trains are suffering teething problems as it seems is just about always the case and much of the unreliability of this offering seems to stem from that - whether it's power failures or frozen water or dicky couplers and one would hope these will in time get ironed out
2: The actions of the operator. It seems to be commonplace that the Railway (not just Avanti) plan on a virtually no contingency basis i.e. that nothing will go wrong. And when it does, then there is time lost or services lost. Simple example: late running inbound train arrives with plenty of time to turn round and depart, but the one and only driver present has to have his mandatory break so the return trip runs late for no other good reason. Example: frozen toilets on a morning where ambient temperatures were well forecast to be below freezing. That should (IMO) have been accounted for, whether by leaving the thing on power or by having a crew available early to warm it up or whatever.
3: Suitability of the route. I think that this has been demonstrated, since it appears that every train that actually ran, ran prefectly well, even if late, with few if any knock-on delays from pathing. If there is one issue here, I'd suggest that the planned timings were perhaps too tight for the type of stock, which appeared to have no ability whatsoever to gain time, even losing the engineering and pathing allowances in the schedule. That is not an issue with the route per se, of course.
4: Need/Usage. I gather that passenger use of these has been relatively good and I think it's well accepted that many people would rather spend extra time on a train than ride on a bus. I guess then that this will be a given.
Of these the only "static" factor is the route and as I say - that worked. The others are down to variable factors which could/should in time be resolvable.
