There is a ~8 mile stretch of double track right of way that runs through my hometown that both CSX and NS use. I'm located in Raleigh, NC, and the track runs from NS's yard in downtown Raleigh west to Cary, where the two tracks split. CSX turns south toward Southern Pines and Hamlet, and NS goes to Durham and other points westward, eventually reaching Charlotte. The CSX track is the old Seaboard Air Line Mainline that ran from Richmond, VA south to Florida. It now sees mostly only local freight trains. The NS track is the old Southern Railway mainline from Raleigh to Charlotte, which connected Southern to points east, reaching the Port at Morehead City.
I live about a quarter mile from this line and work right across the street from it. It's in plain view out the window of my office at work about 50 yards away.
NS seems to be much more active here, about 10 to 15 trains a day. Most CSX activity here is local, about 6 or so a day. Also, this line is used by about 4 Amtrak trains a day. Looking out the window of my office at work, I have only seen a CSX and NS train in the same field of vision once or twice in the past few months.