NEW YORK--(BUSINESS WIRE)--Kroll Bond Rating Agency, Inc. (KBRA) is pleased to announce the assignment of preliminary ratings to 15 classes of the CGCMT 2015-GC31 (ratings list below). CGCMT 2015-GC31 is a $723.3 million CMBS conduit transaction collateralized by 50 fixed rate commercial mortgage loans that are secured by 76 properties. The pool balance of $723.3 million is the lowest among all of the conduits KBRA has rated to date. The properties in the collateral pool are located in 26 state