Just had a look at the West Mercia SCP site (
http://www.speedaware.org.uk). On the FAQ page, note this Q&A:
What happens if the scheme is so successful that fewer people speed and there is insufficient revenue to cover the extra camera costs?
In the short-term, should the costs exceed the revenue, the shortfall will be met by the Partnership. If this does happen, there will have been a very significant reduction in the number of people killed or injured on our roads. This will save far more in medical and social costs, apart from the misery and suffering that will be saved, than the loss in revenue. The benefits of camera enforcement could therefore be recovered from savings made elsewhere, and corresponding changes to camera funding arrangements could be made. As compliance improves, camera use may be reviewed and scaled down as appropriate.
Note that in the the first instance, "the shortfall will be met by the partnership". This means the four local highway authorities of the Borough of Telford & Wrekin, Herefordshire Council, Shropshire County Council Worcestershire County Council, The Highways Agency, West Mercia Constabulary, West Mercia Magistrates’ Courts Service and the region's six NHS Primary Care Trusts, all of whom receive the vast majority of their funding from local and national taxes. And, of course, with the "partnership" being at several arms length from democratic accountability, getting a say in this is near-enough impossible.
Scaling down cameras is, of course, the last option to be considered. Those who advocate starving the cameras of cash should note that the authorities have thought of that one already.