When I was in New York I sat in some unbelievably cool carriages on their subway, and yes, I know ours is older, but it's not that much older. Even in the early part of the 20th century New York's subway had fans in the carriages (see photos from my New York Transit Museum trip below)
I seriously don't remember seeing any fans in old carriages in our London Transport Museum. Did we ever have them? Or was there some sort of health & safety reason for us not having them?
Oh well, look forward to the carriages when we eventually get them in three years time.
Update - For those who like such things a mock up of the new trains will be on display at Euston Square Gardens for everyone to view from Saturday 26 September to Thursday 2 October. "Passengers will benefit from air conditioning, walk-through carriages, CCTV coverage in each carriage and improved accessibility." See the press release from the GLA for more & Londonist have got some picture of Boris "admiring the spacious interiors of the new carriages".