>> which can be filled by anyone who wants to run fiber through them.
No, there is only so much space in the pipe. It has a limited capacity so the next logical step is to charge for access.
>> Personally I'd rather they put the fiber in themselves and lease it out...
At that point why not just have the government be an ISP an route any and all packets that come their way? See, they're proposing to take care of the hard part - digging and laying the pipe - on behalf of companies. The biggest companies will have the least trouble filling those pipes with light pipes.