I believe that in amsterdam, even though you only have 1 fiber line running to your house, you can choose from many ISPs over that line. Since (I assume) google is not installing an entirely new fiber network, but merely buying fiber rights and doing last-mile construction, it seems like that would also be a reasonable framework to establish here.
I'm not saying it would be easy. It would take a lot of legal work. But if google's missions to not be evil, and disrupt the ISP market are to believed, they could make it easier.