An investor group headed by private investment firm Equity Group Investments (EGI) that includes International Rail Partners LLC (IRP) recently pooled more than $200 million to help IRP form RailUSA LLC.The new subsidiary already is helping IRP acquire regionals and short lines. In August, RailUSA completed its first acquisition: Grenada Railroad LLC, which operates a 206-mile line between Memphis, Tennessee, and Canton, Missouri.