Can you qualify those claims? Who would make a journey by HS2 who wouldn't have travelled by the existing fast services? HS2's own projections rely heavily on the transfer of existing passengers to HS2 and on leisure travellers who will not want to pay premium fares. The passenger numbers claimed by HS2 would only be achieved if you PAID people to ride it!
As for operating costs, projects of the magnitude of HS2 always have expensive teething problems and are typically into first maintenance before the problems are sorted. The slab track favoured by HS2 costs twice as much initially, saves a lot on maintenance in the early years, then a heck of a lot when it has to be replaced, as the Germans have found.
To put some numbers to those claims, what needs more coaches, running 16 coach HS2 services between London and Manchester or 11 coach existing trains?
At first glance it's reasonable to say that HS2 needs more as the services are 5 coaches long, however what's the actual answer?
First off you need to look at how long it's going to take before you can use a train for the following services from a given location.
Currently from leaving (say) London to bring able to leave London again having gone to Manchester and then come back takes 5 hours, with HS2 it'll be 3.
Therefore at 3tph you'd need 15 sets currently and 9 sets with HS2.
15 sets with 11 coaches in each is 165 coaches, whilst 9 sets with 16 coaches in each is 144 coaches.
In reality currently there's a mixture of 9 and 11 coach sets, so the difference is closer. However many suggest that the alternative to HS2 is that we run 12 coach sets, that would make matters much worse at 180 coaches.
Given that (historically) the leading of coaches cost £100,000 each, even a saving of 5 coaches is a saving of £0.5 million a year.
However with much more capacity on a HS2 service (broadly the same as a 9 and 11 coach set combined), there's plenty of extra seats to be able to sell at a lower price to still generate the same money.
The time saving also reduces staff costs, as a driver and guard on a 6 hour shift could do 2 return runs with a ~30 minute break at each end, rather than just 1 on a 5 hour shift. As such, whilst you've increased the time working by 20% you've doubled the number of passengers the driver is carrying (even if there's no extra people on each train).
If the staff costs are effectively reduced by 40% (and typically staff costs make up 1/3 of TOC costs) just that alone could allow a £100 ticket to be reduced to £90 and the TOC still make more money.
Whilst maintenance could be more expensive, track access charges are measured in pence per mile, even at 30p/mile/coach on a 200 trip that's a total of £960 for a 16 coach set.
That's, at 50% loaded, a total of £2/passenger (some of which would be being paid anyway on the existing sets).
HS2 predicted a 1% shift from air, that doesn't sound much, but could be 1 million people. Likewise the 4% from road travel could be 4 million people. However many anticipate that there's are conservative estimates, given that there's 6 million air passengers between London and the Central Belt of Scotland each year and currently rail is a little slower city centre to city centre.
Now whilst half of those are making connecting flights at London, that's still 3 million who could use rail fairly easily, with the time advantage switching from flying to HS2 being marginally quicker and the potential to reduce ticket prices a little (as well as giving better connectivity to parts of the South East via Old Oak Common and maybe carbon taxes becoming more likely for flying) and there could be a significant switch from flying in that route.
There's then other routes which could also see people switch to rail from flying, which in turn could make such air routes less viable (but at least slightly more expensive as the costs are split between fewer passengers).
Even without carbon taxes, people are becoming more aware of the impact that their choices have. It's been calculated that for every 1kg of CO2 produced it results in 2,400kg of ice melting, and as such the less we produce the more ice which can be retained. As such even small changes like walking 2 miles a week rather than driving over a year is (assuming the numbers are right) a retention of 125m3 of ice.
That may sound a lot until you realise that there's 30 million km3 of ice in Antarctica alone. Whilst it's a small figure, that just one person, however if enough people did it out could be enough to keep enough of the ice sheet that there's actual assume left.