It was several airlines. Some complained about the data being available to the public, others didn't like their flight plan data being easily accessible by their competitors, All in all apparently enough to restrict access to that kind of data. That said, can't be really all that hard to provide the information to the flight crews?
We usually get the Eurocontrol slot message routet directly to the flight deck printer, which makes it quite accessible to us. And the Eurocontrol website is still open where you can see flow measures across the ECAC space on a sector basis if you really want to see more.