Genesee & Wyoming only experienced a few days of controlling RailAmerica’s rails in 2012 due to approval of the merger by the U.S. Surface Transportation Board that didn’t come down the pike until Dec. 28, and it is the hope that the acquisition will offer improved volume numbers for January. Without RailAmerica, GWR saw a 9.1-percent year-over-year decrease in December traffic — volume fell 7,480 carloads from last year’s total of 74,529 carloads — on its way to a quarter-end...