There is a derogation from the Freedom of Information Act created specifically for the BBC. When the new bill was wending its way through Parliament, the BBC and Channel 4 complained to the Home Office that they would not be able to do their job properly if covered by the Act. They argued that, if for example their journalistic sources were compromised, they would no longer be able to collect important news stories. They didn't mention Robert Peston acting as a receptacle every time a minister wanted to make a diversionary leak, but that kind of activity would also presumably have been threatened were the corporation to fall under the Act.
In the event, a compromise was reached and the derogation was written into the act, exempting the BBC from its terms but only regarding "journalistic and artistic" activities. At the time it was agreed that this would cover all of the day-to-day activities of the BBC. See here.
With depressing predictability, the BBC, those lovers of freedom of information, have now set about expanding the scope of the derogation as far as they possibly can. The meaning of "journalistic purposes" has been expanded to cover editorial policy, reviews of editorial and journalistic performance and a host of other activities that can't possibly have been the original intention of Parliament. The Information Commissioner (ICO) has sat back and accepted all this.
Even where an activity is known not to be covered by the derogation, the BBC routinely claims that it is. The ICO has managed to show his teeth on the subject of the BBC's finances, which he has ruled are not covered by the derogation. And does the BBC care? Take a look at some of the decisions of the Information Commissioner.
I could go on, but I think you get the drift by now. You have to remember that decisions of the Information Commissioner carry the full force of law: they are equivalent to the decision of a judge. So for the BBC to continually argue that financial information it holds is not covered by the Act can only be described as contempt of court. The powers that be at the BBC clearly feel that the law can safely be flouted, and continually so, without the slightest fear of any comeback.
And meanwhile the Information Commissioner doesn't even raise a squeak of complaint. And why not, we might wonder? It's speculation, but perhaps the BBC and the ICO are both happy with the arrangement since both sides can keep themselves comfortably employed, bloated pensions fed by the poor unsuspecting licence fee payer and the poor unsuspecting taxpayer that they both wilfully ignore.