Public Accountability for Public Services
If a service is paid for by the public purse, then there should be public accountability: and that does not mean 'reviewed' by a committee of unelected civil servants or advisers. It should be a matter of fact that operation of public services requires FoI transparency, which is not trumped by commercial confidentiality.
Perhaps there should be a judicial test, that if the service would be required to release FoI information when operated by government, then it should be required to release the same information when outsourced, whether to a commercial provider, or to a QUANGO or NDPB - you should not be able to escape scrutiny by outsourcing.