This is a pretty classic network operator story: go to great lengths to provide for physically diverse paths, then not notice when your provider refactors and grooms them onto the same bundle.

In NL this often happens because of waterways. All starts off with good intentions, multiple providers, totally different fibers exiting the building in different directions. And then they have to cross a canal or a river. It's a 50/50 at that point whether they converge on the same conduit across the water.