It wasn't only council staff in on this. So were some councillors.
Mike Davidson who chairs the council's urban development and transport committee was worried it would be confusing to the public.
He didn't think it was wise to release the report during the "funny season" for councils. The funny season is the election period. Better, he said, to "park it and let the new council decide".
With that one remark, Davidson probably revealed the real motivation for keeping the document secret. For councillors, the risk of losing council seats. For council staff, the risk of their plan being scuppered by angry ratepayers.
The elections are in October. This is a high-risk time for councillors who run against the grain of public sentiment. Most of the time they get away with blue murder around the council table. They support unpopular ideas, comforted by the knowledge that the worst they'll reap is the angry fist-shaking of a few ratepayers who bother to consume enough news to know what's going on.
But right now, the fist-shaking can turn into something more meaningful: a vote against them.
And not only is it a high-risk time, it's also a high-risk topic.
Transport is controversial. Few things drive people more barmy than politicians making life harder for motorists. Auckland City Council's hope that Aucklanders would walk any trip under 6km drove talkback for days. The National Party has accused the government of declaring a war on our cars.
Of course it would suit the Mike Davidsons of this world to park the tough calls for the next council. He probably banks on the next council looking very similar to the current council given ratepayers often vote for recognisable names. Often that's because they can't remember what councillors actually stand for.
So leaving it for next year would probably mean the same councillors would still get to make the call they want to make but avoid having to answer to ratepayers for it. At least, not for another three years, by which time many will have forgotten the draft plan.
In the end, we do know what is in that plan. Two councillors - Phil Mauger and Aaron McKeown - went to the media to force the council to 'fess up. They were, in turn, accused of scaremongering and pulling an "election stunt". Of course that's what they did. But an election stunt is a lesser crime than trying to hide information during an election period.
Those who tried to hide the plan deserve public opprobrium.
They'd do well to remember they work for the ratepayers. And ratepayers would do well to remember that too, and use their votes accordingly.
• Heather du Plessis-Allan Drive, Newstalk ZB, 4pm-7pm, weekdays.