There are certainly many benefits to employing maglev technology in the UK.
For example it can accelerate like a tube train (or faster!) all the way to 500kph because the traction power is not constrained by weight limitations in the vehicle.
Chuo Shinkansen accelerations are limited primarily by passenger comfort, sustaining values above 1.1m/s/s pretty much all the way to max speed.
Stopping from 500km/h, holding doors open for a minute and accelerating back to 500km/h costs you only about 3 minutes! The operational implications of such capability are pretty clear (what if the tube went to Manchester?).
But all this is rather off topic so I won't derail the thread, I would start another but last time I tried noone was interested in discussing it!
I suspect in part because most are likely to be conservative about it and would rather see something like HS2 which can see rail services continue beyond the extent of the new infrastructure without having to change trains.
For example HS2 improves journey times to (say) Liverpool even though the line doesn't actually go there. Unless you can connect to a line with tube type frequencies the improved speed would likely be lost by having to change trains.
If you double from 60mph to 120mph that cuts the journey time (120 mile trip) from 2 hours to one hour, double again to 240mph and it reduces to 30 minutes, however double it again to 480 and it reduces to 15 minutes.
However if you then need to finish off by changing trains even a 5 minute change time wipes out much of that advantage.
Whilst HS2 does deal with longer distance and so the savings could be greater, even at 240 miles (London to Blackpool) whilst that could be done in about 30 minutes, if the infrastructure doesn't actual go there then the time savings soon get reduced quite quickly just from changing trains, let alone if the local service is slower.
Also isn't there complications with junctions, meaning that most routes to date are simple point to point systems?
Whilst some opposed to HS2 would suggest that they would be better, the benefits are more limited, especially given the main purpose of HS2 is about capacity (the speed is there to ensure that the capacity is actually used and to mean that the trains can be longer without actually needing more rolling stock than is currently required, or at least not much more).
As I've highlighted before, if all the 390's were running around with 12 coaches with around 660 seats (an often cited way of increasing capacity for the WCML) or even an 11 coach 80x with around 825 seats (only 70 of which are first class) they would need more coaches to do the London Manchester run than a 16 coach HS2 train.
11 coaches taking 5 hours to run London, Manchester, London and New ready to run back Manchester again, at 3tph would require 165 coaches.
HS2 would reduce that from 5 hours to 3 hours, so due the same frequency but with 16 coaches per train it would require 144 coaches.
Meglev (assuming the London Manchester journey times is 40 minutes) would reduce the round trip time for the ruling stock to 2:20 (mostly as the turn around times are n't score to be reduced compared to HS2 or even classic trains). To run a 16 coach train would require 112 coaches (however that only really works so well as the service is 3tph.
Arguably because of that reduction in rolling stock you could run longer trains, however it's already expensive enough to build 400m long platforms, so longer would add further costs. Especially if you started to need to add moving walkways to reduce the walk time for (say) getting the 500m from one end of the train to the other or even to the middle as you try to get to where you're going.
I'm not saying that the technology wouldn't every be built, however it's probably better to build HS2 increase general rail usage because of that and then be able to justify ultra high speed rail (UHS) because there's already a lot of demand for rail.
It could even be that UHS1 is built London to Edinburgh (East Coast) to relieve capacity issues with HS2 and remove the need for any flights between London and the Central Belt.
By doing so it wouldn't render HS2 obsolete, it may remove the need for the London Scotland services, but they could be used to increase the number of HS2 services to (say) Liverpool.
Therefore, there's as good chance that even if UHS was delivered in the UK then HS2 would still be beneficial to be delivered.
