To the best of my knowledge there is only one operating unit painted for the I&O on home rails and that resides on an isolated line they run south out of Logan, Ohio. Much of their older power sits in the dead line in McCullough Yard in Norwood, Ohio. This includes their GP9's, GP30's, and GP35's. Their new power, mostly made of of GP40-2's and SD40-2's, was transferred to the DNGO in Texas a few years back.
The I&O's current operating mainline roster includes a about a half-dozen ex-BN GP50's with IORY and CBNS reporting marks, three SD70M's on lease from the Susquehanna, two leased SD45's painted for Wisconsin Central (although they might be on the I&O through a dealer), two SD40T-2's and one SD45 from the Southern Pacific by way of CEFX, an ex-UP SD40-2 from CEFX, three SD40-2's in the old RailTex coporate scheme with IORY marks, and at least one ex-BN GP40-2. There are probably a number of other units that I missed that only operate on the tangle of branches operated in southern Ohio and Indiana and never see any time on the I&O's mainline to Flat Rock.