This will almost certainly fail
Atos is not a bad company, but the Microsoft involvement is a concern because it's thus unlikely the Gateway will be really enabling Open Standards, thus disenfranchising an ever growing part of the population (let's call them the Vista rejects).
The Government Secure intranet (GSi) is now over 10 years old, and that has worked from the day it went into pilot. Why? Because it was based on Open Standards. Ever since its inception, however, it's been a battle to keep core services that way because the moment a proprietary vendor gets its claws in this it amounts to giving them a blank cheque. So a huge battle followed where the then CCTA formally opted for Open Standards, only to be completely ignored because ex Government people now worked for Microsoft and convinced their buddies it would all be OK (logically, that's why they get the job at MS in the first place).
Well, I presume the vast number of failed Government projects hasn't been educational enough. I hope Atos can work past the problems they'll inherit by using lock in strategies.