eltonioni, thanks for the information. I wasn't aware of that, and no-one else wasn't forthcoming with it (even the FSB).
You make a comment that "Without the airport there was no business park", but it also sounds like without the business park there was no airport, as you do say that the business park will pay for the airport.
So the FSB's campaign is based around potential shortcomings in a contract drawn up 20 years ago by the SDC. That's not unusual or illegal (public organisations have never been good at getting involved in commercial contracts).
An inquiry wouldn't have the power to right any wrongs, as that would involve changing/revoking perfectly legal contracts that have been signed since then. Only a court would have the power to do that, and a court would only do that if there was criminal activity - which no-one has suggested.
An inquiry would cost hundreds of thousands/maybe millions for everyone involved (including Sheffield City Council, who can hardly afford it at the moment) just to tell people what they knew all along, but with no power to change it. The only winners will be lawyers.