The minister always has a fat file, constantly updated at an indeterminate cost to the taxpayer. As Paddy Gourlay suggested in The Canberra Times last year ministers keen on cutting expenditure should "consider more closely the costs and consequences of parliamentary, media and other briefings they request, and just how much of that ends up being of any use - there would appear to be ample scope for better risk management here."
In any event I'm sure most involved probably don't realise they are engaged in highly sensitive work that potentially raises weighty issues of parliamentary privilege.
Yes, under access to information laws in Queensland, WA and NSW briefing notes on contentious issues, possible parliamentary questions or PPQs in some parlance and House folder notes to others, have been found to be exempt from disclosure or contrary to the public interest to release because to do so would infringe the privileges of parliament.
The privileges of parliament are an arcane subject that takes us way back to 1688.
I expect, if we could check, that the leaders of the Glorious Revolution would be highly amused to learn that the spirit of that year is invoked to favour non-disclosure of information prepared by public servants for possible use by the minister to answer questions that may or may not be asked. Or at least some that I've seen in my day.
Despite these rulings there are instances where question time briefs have been released without fuss. As far as I'm aware parliament wasn't outraged and no one complained of a limitation on freedom of speech. Whatever would they have made of that in 1688?
In Western Australia in Re Saffioti and Minister for Transport; Housing  WAICmr 10 the applicant Ms Rita Saffioti MLA was denied access to "contentious briefing notes" and emails sent internally between the Minister’s staff and emails from those staff to staff at the Premier’s and other Ministers’ offices on grounds that public disclosure would infringe the privileges of Parliament. The information in question was directly referrable to ‘proceedings in Parliament’ because the documents were prepared for the purpose of, or incidental to, the transacting of parliamentary business. Disclosure would infringe upon Parliament’s power to control the publication of documents and information incidental to transacting the business of the Legislative Assembly. Only intentional and general waiver of parliamentary privilege may be taken into account when applying clause 12(c).
Two relevant Queensland decisions concern the now repealed Freedom of information Act. In Re Stiller and Department of Transport  QICmr 8 the Information Commissioner found the Ministerial Briefing Note constituted an act done for the purposes of, or incidental to, transacting business in the Assembly and was exempt under section 50(c)(i) of the FOI Act.
Similarly the finding in Haneef and Department of Police (Unreported, Queensland Information Commissioner, 24 February 2010) regarding a parliamentary briefing prepared to assist the Police Minister to answer questions that might be asked. Release of the briefing, other than in accordance with parliamentary processes, would infringe the privileges of Parliament.
In the NSW Administrative Decisions Tribunal in Tziolas v NSW Department of Education and Communities  NSWADT 69 the information withheld consisted of speech notes and a briefing for the Minister included in a 'House Folder Note.' The Government Information (Public Access) Act states that there is a “conclusive presumption that there is an overriding public interest against disclosure of any information the public disclosure of which would, but for any immunity of the Crown…infringe the privilege of Parliament” ( Section 14 table clause 4(c)).
The NSW Parliament has not enacted comprehensive legislation setting out its powers and privileges similar to that enacted in other jurisdictions. (Parliament's website has a summary.) Judicial Member Isenberg in Tziolas cited a Supreme Court decision in a case concerning s16(2) of the Parliamentary Privileges Act 1987 (Cth), which defines “proceedings of parliament” for the purposes of Art 9 of the Bill of Rights 1688 to mean
all words spoken and acts done in the course of, or for purposes of or incidental to, the transacting of the business of a House or of a committee, and, without limiting the generality of the foregoing, includes:Austin J In the matter of Opel Networks Pty Ltd (In Liq) (2010) 77 NSWLR 128 had identified "frank and candid" type principles to support a decision that briefing notes should be privileged from production in discovery in accordance with s 16 [at118]:
(a) the giving of evidence before a House or a committee, and evidence so given;
(b) the presentation or submission of a document to a House or a committee;
(c) the preparation of a document for purposes of or incidental to the transacting of any such business; and
(d) the formulation, making or publication of a document, including a report, by or
pursuant to an order of a House or a committee and the document so formulated, made or published.
... It seems to me necessarily true, and not dependent upon the evidence of the particular case, that if briefings and draft briefings to Parliamentarians for Question Time and other Parliamentary debate are amenable to subpoenas and other orders for production, the Commonwealth officers whose task it is to prepare those documents will be impeded in their preparation, by the knowledge that the documents may be used in legal proceedings and for investigatory purposes that might well affect the quality of information available to Parliament. ...The Tribunal in Tziolas  accepted a submission by the Information Commissioner NSW that those principles and the fact that in contrast to discovery and subpoena, disclosure of information pursuant to the GIPA Act must be unconditional, were relevant to the scope and application of clause 4(c). And that there was an overriding public interest against disclosure.
(All you ever wanted to know about legal privilege in the context of parliamentary proceedings in this AAT decision by Deputy President Forgie.)