Its a cynical world...
To be fair to our political masters (not that I'm normally a fan), the timing of this announcement is quite clever, not just to avoid people realising how long its been since the last order*, but also because there is very little in the news at the moment (Prince Phillip out of hospital, a shooting in Salford, a stabbing in London, nothing that would be *huge* news in a "normal" week), so the coalition get a "good news story" into the press, its been repeated in several bulletins I've heard today (radio/telly).
Maybe later someone will do the maths, realise its been a thousand days, maybe question why it costs well over £1,000,000 per coach, wonder why the busy London routes these EMUs will be used on require such huge subsidies, start to question why our fragmented railways are so expensive that they need such money throwing at them... but for now, Greening can bask in the positive headlines (no Labour MP is going to question why this is costing so much, because it'd be unpatriotic to question throwing all this money at Bombardier...)
(* - strange, considering how many electrification announcements we've had in the last couple of years - as it we don't need new EMUs to run on these newly electrified lines!)