The south bridge, showing in your pic, was for the east and west mainline tracks.
The north and the centre bridges were close to being the crests of the two hump (east and west) operation. The north bridge connected the long gone westbound arrival yard between Howard Ave with the westbound hump west of Dougall which we used to call the class yard when that was all that was left. Then, tracks classified for Detroit and west were pulled into the Electric yard and others for CPR and ETR interchanges etc. The centre bridge connected the eastbound arrival yard (tracks 35 to 39) with the eastbound hump, east of Dougall. Trains from Detroit would enter the Electric yard on the south half (that was torn out years ago but still showed faintly on the board in the Windsor South depot office) and be shoved into or pulled directly into the eastbound Arrival yard and then be humped (over the middle bridge) toward Howard Ave. Hope this helps.