This sounds like an extetension of the scheme which has been operating, just east of where you refer to, for over a year:
http://www.timesonline.co.uk/article/0,,2-1565 657,00.html
Mobile cameras are used, on bridges over the motorway, so it's impossible to list exact locations.
Most new speed camera systems, however, use 'speed averaging' cameras, which are placed at 1 mile intervals and record the average speed over that distance. The A14 has had them for years. Hopefully, they'll eventually be introduced along the full length of all motorways and major trunk routes.
Chris