I know my knowledge on this subject is small compared to others' here, but I would not think that CTM would abandon the whole line unless General Iron closes. I think Big Bay , Sipi Metals and General Iron are all relaying on the cheap rail transport much more evenly in proportion to how much CTM relies on them for business. In my opinion if both both Sipi and Big Bay would close (I'm not even suggesting I want this to happen,) CTM would keep it open for General Iron. As CTM has few grade crossings and an overall shorter route to General Iron, and given the amount of material General Iron ships out, I think it would be highly unlikely for them to quit as long as General Iron is there.
On an unrelated note, if you go to street view on 1398 W Le Moyne St and look towards the yard, you can see a tank car that I am pretty sure was for Peerless.