Average speed cameras on the A3 and M3

Within the past week average speed cameras have been installed on the A3 south of Guildford to the Milford turn off-both North and South and also on the M3 from the Bagshot to Farnborough junction,again in both directions.The spped in which the work was done,closing off one lane and they seemed to work over night,almost seems suspicious.Are ther number plate recognition cameras also added.Both stretches of road are not particulary accident prone.Does anyone know anything more?