NEW YORK (Standard&Poor's) May 1, 2015--Standard&Poor's Ratings Services today assigned its 'B-' issue-level rating to Boulder, Colo.-based fiber infrastructure and colocation provider Zayo Group LLC's proposed $350 million unsecured notes maturing 2025. The recovery rating on the debt is '5', indicating our expectation for modest (10%-30%; upper half of the range) recovery for lenders in the event of default. At the same time, we raised the issue-level rating on the company's existing senior unsecured debt to 'B-' from 'CCC+' and revised our recovery rating on this debt to '5' from '6'. The revision of our unsecured recovery rating reflects both an increase in our net enterprise value under our hypothetical default scenario and increased residual value