So if they don't publicly out the report, then the odd's of it staying contained out of public eye are pretty darn high.
The only area in which they could curtail it's release would be if some terrorist type factor or related activity that they could class in that catch-all definition. But even then, details will emerge and it would only delay its publication to fulfill their contractual obligations (think mobile telcos and large business that contract network capacity and links from them with lovely contract SLA's).
The fact that they have a lot of egg on their face after a similar outage in 2012. Heads will roll over this one and politicians will certainly want answers.
Unfortunately, I don't know of any such actual democracy.
https://www.nu.nl/internet/2779095/onderzoek-112-storingen-k...
They will probably have to do one under government pressure, but it'll be so heavily NDA'd that no one will ever read it.