Surprised to see a thread on this here, but should my opinion on this not already be easy to guess I think this is an awful idea for the following reasons:
i) Its a ten-year (though in reality it is going to be longer since the company involved will already have all the trained staff, all the experience and probably most of the facilities required so its not as if people will be able to outbid them down the line) monopoly that is on offer, not the creation of an actual market in police services.
Such a market could have brought about by allowing the staff in each force (and/or each role within that force) to form their own companies and bid for both their own and other forces contracts, plus of course smaller-scale companies would be much easier for the non-police private sector to set up and compete with the ex-police ones (and easier to fix when either type of company went wrong). If they had done that, then we would be much more likely to get costs down, improve efficiency, innovation and competition generally than this monopoly will be able to.
ii) It wont result in any savings and will probably in fact cost a lot more than it does now - the way the contract is written will inevitably mean that the private company has to rely on the police staff who will be "transferred" from the various constabularies to carry out the work they have contracted for, staff who obviously will have a powerful incentive and the means (since they are mostly unionised, and its not as if many of these roles have an equivalent in the private sector that they can bring people in from to scab) to resist any change in wages, pensions etc being imposed on them by just walking out on strike and causing the system to collapse.
The government has already tried a similar deal with "privatizing" (though again what they in fact did is offered a monopoly to a private firm when the service had previously mostly been provided by private, uncontracted but registered individual interpreters who were only paid for work performed) the Court Interpreter service, which is now costing a lot more than it used to because the interpreters refused to sign up to the new deal - not unreasonably, because their rates were cut by half. As a result, what has happened is that the MoJ now has to pay both ALS and
the "rogue" interpreters, otherwise the legal system collapses.http://www.guardian.co.uk/law/2012/mar/02/interpreters-courts-protest-privatised-contract
iii) Quite a few of the people behind this proposal are very senior ex-police officers, and its only being actively supported by people of the same very senior status. As a result I have a hard time believing that this isnt more about graft than it is about "efficiency".