Crossrail is coming. It will run from Maidenhead, Oxford and Heathrow through central London to Essex and Kent. It will use mainline style trains, each with 9 air-conditioned carriages. At peak times, 10 trains an hour (in both directions) will stop at Ealing Broadway. Some of these trains will also stop at West Ealing and Acton Main Line with a few more stopping at Southall. Hanwell will get just 2 trains per hour.
The Crossrail programme is being run by Crossrail Ltd. This is now a wholly owned (but autonomous) subsidiary of Transport for London. There will be a whole series of contracts to implement various parts of the programme. Work on the tracks and stations on the existing surface railway (such as at Ealing Broadway) will be carried out by Network Rail, or by their contractors.
Some work on the Crossrail programme has already started. The bulk of the construction is expected to take place from 2010 to 2016. A limited Crossrail service may commence in 2017 reaching Ealing in 2019.