What is the reason for asking the question? The 397s have only just entered service on a route they have specifically been procured for = eight diagrams for Manchester to Scotland and two for Liverpool to Glasgow.
If there was a real downturn in travel long term, there could be an argument for only running 1tph between Preston and Glasgow - ie the London - Trent Valley - Glasgow service. The 397s wouldn't then be needed as Northern would cover the demand between Preston and Manchester and between Preston and Liverpool. But if that happened there would be loads of spare rolling stock and I'm not sure the 397s would have any future.
Yes, or indeed, if there were major cut backs on Avanti, one possibility would appear to be running a Euston - Birmingham - Manchester - Scotland service combining the second Birmingham and Manchester service from Euston and removing Cross Country completely from the Birmingham to Manchester route and TPE from the Manchester to Scotland route. The bare minimum Avanti service would be something like 1tph Manchester direct, 1tph Liverpool direct, 1tph Glasgow direct, 1 tph Birmingham and 1tph Euston - Birmingham - Manchester - Scotland.