My suggestion would be one company is going to control ALL the fibres that go through a particular section of conduit, adhering to some strong guidelines regarding the management, that way there's one company to blame, and not an anarchy of 100 companies to fight with each other and damage each other's cable. That way they could just put in one huge run per conduit, and no need for 100 small pipes wasting precious space
The plant-managing carrier for that segment of conduit can manage all the individual physical fibres as they like, provided they meet Service Level Availability requirements and Repair/Re-splice performance requirements, But set their legal requirement such they must Be a carrier that sells _ONLY_ Physical plant access in that area (Not related to any entity selling IP services) and _Only_ to licensed Layer-2 transport providers who have signed agreements which include L2 providers will provide services offered equally to competing ISPs, and Fair Reasonable and Non-Discriminatory Pricing for all involved, Must use field muxing technology such as DWDM on each fibre. The number of possible Colors Times the number of Installed and tested strands is considered the installed fibre circuit capacity.
The plant management carrier will not lease, rent, or offer more than 25% of the available circuit capacity at any given time to any one Telecom/ISP or to any one customer, to maintain compliance the total calculated available capacity must be reduced if it is found a fibre or color is broken or out of spec, and not repaired within a 72 hour grace period, also if two customer ISP's become related such as in an acquisition, the two providers must surrender enough capacity to keep their total below the 25% for each conduit segment...
And any particular L2 carrier may not offer more than 15% of their provisioned capacity on any segment as a dedicated, guaranteed, or priority network connection particular to any 1 customer or group of customers, the rest must be shared and available equally to all customers and applications, and the L2 carriers may not discriminate or refuse to sell services to any customer who is willing to commit to at least 1 year service 10 Megabits or higher, the L2 providers may not restrict, throttle, Randomly drop or refuse to forward any frames, or charge different prices per Gigabit purchased, except for cases of more than 100% usage of Purchased datarate, and 95th-percentile promised burst capacity usage: the L2 transport providers may not discriminate based on size of customer network, whether the customer is residential or a business, link speed purchased, cumulative number of bytes transferred, contents of packets, etc. The only allowed traffic management by L2 providers is to set a limit on the total maximum Datarate that any single one of their customers will be allowed to purchase --- the L2 providers should be required to expand their capacity or reduce their existing offerings on any conduit segment where purchased offerings advertise in peak burst datarate exceed 2000% of the bandwidth they have physically provisioned,
or where base datarate or the sum of Top-line rates or for "Whatever claimed service speed or most-prominently listed speed is in advertising materials" for purchased services over a segment exceed 800% of the physically provisioned bandwidth available to those services.