The investigation cannot advance to a full public inquiry without the cooperation of MPs, which seems to be in doubt.
In November 2009, the then Opposition Upper House MP Duncan Gay sniffed something very wrong about Mr Obeid buying land in the Bylong Valley over which a coal exploration licence had been granted by his friend, mining minister Ian Macdonald.
Mr Gay took action under what is called Standing Order 52, a rarely used but powerful tool that allows MPs to command the bureaucracy to hand over documents.
In this case it was a call for papers from all government departments about what Mr Macdonald and Mr Obeid were doing.
The Premier at the time was Nathan Rees. A week after the call for papers, Mr Rees sacked Mr Macdonald.
On November 26, the public service replied that it had complied with the call, supplying Parliament two boxes of papers.
Those documents have been held in storage at Macquarie Street ever since.
It is not clear what assessment Mr Gay made about the papers he demanded to see; he will not talk about it.
It was only recently that questions were raised when Upper House MP for The Greens, Jeremy Buckingham, compared the files to what was becoming public at the ICAC inquiry into Mr Macdonald and Mr Obeid.
"I was very surprised that there were so few documents - maybe a few dozen documents," Mr Buckingham said.
"That's what concerned me: how few documents were provided, and then I watched the ICAC investigations unfold, and obviously, there's just a wealth of information spilling out of that and it's of enormous concern to everyone."
Mr Buckingham says it would be unprecedented for documents not to be provided by the public service to Parliament.
"This is a very serious matter. It's one of the key weapons in the arsenal of Parliament to get to the bottom of issues, to discover how things have occurred," he said.
"The Standing Order 52, the call for papers, is one of the real strengths of Parliament.
Mr Buckingham appears to be in a strange minority on that score.
But on Tuesday it foreshadowed another response altogether that could stifle inquiry, and possibly shut it down altogether.
Mr Gay revealed that should the ICAC come calling, it will not get the boxes.
Instead, the request will be put before the Privileges Committee to inquire and report.
"It is ultimately for the House itself to determine whether its order for papers has been complied with," he said.
Called to account
No-one on the Labor benches uttered a word of protest at the announcement.
A referral to committee is a process that could set back ICAC's ability to investigate by years.
Mr Gay declined to explain why that is in the public interest.
Mr Buckingham says its urgent ICAC be given the documents to assess for itself why papers were withheld, and by whom.
He says senior public servants still serving government must be called to account:
"All the directors-general of all the departments sign off saying that, to the best of their knowledge, these are all the documents, and it concerns me that some of the state's most senior bureaucrats, that the Premier's Department, could look at so few documents and think that that is all that existed," he said.
"So at the very best, it may be negligence; at worst, it could be part of what is a very, very serious cover-up."