Pretty interesting. I'd be cool to have one that showed the cables on land too. I wonder if there's a tool like that, be useful to plan where the best connectively is if you are building your own datacenter for example.
Much of who actually 'owns' fiber in a region is opaque for competition reasons. You have the company that actually laid the cable, then you have companies which may have purchased a few dark strands or IRUs in the cable, then you have a myriad of companies that are leasing dark and installing their own DWDM systems.
Where you can get access to dark also depends on geography and opaque business relationships. There's a lot of places in the US where a 288-count fiber cable goes through but here's no regen hut or POP built to access it. You need you build backwards or forwards along the path to get to the nearest place with active electronic equipment.