BOULDER, Colo.--(BUSINESS WIRE)--Zayo Group Holdings, Inc. (NYSE:ZAYO), a global provider of Bandwidth Infrastructure services, today announced plans to extend its long haul dark fiber network between Atlanta and Washington, D.C. The network expansion will add more than 800 route miles to Zayo’s owned long haul network, which spans more than 19,000 route miles. Zayo will break ground beginning the third calendar quarter of this year and expects to complete the route in the fourth calendar quart