ERCOT (Texas electrical grid system operator) is essentially a mutual company/co-op structured as a non-profit, very similar to muni broadband.

"ERCOT is a membership-based 501(c)(4) nonprofit corporation, governed by a board of directors and subject to oversight by the Public Utility Commission of Texas and the Texas Legislature. Its members include consumers, cooperatives, generators, power marketers, retail electric providers, investor-owned electric utilities, transmission and distribution providers and municipally owned electric utilities." [1]

[1] http://www.ercot.com/about

Yes, that sounds like an ideal organization for connecting municipalities that own right of way and own or eventually take ownership of the fiber on their poles.