At this point I don't think you can not use the leaked map, we've become so reliant on it.
I thought that was the actual Bacchus bridge across the Dakota, the bit you've highlighted runs parallel to the river a bit further up. You got me confused because I was looking at that shot a few days ago for any hint of Old Fort Wallace on the left, which I assumed was hidden behind that rocky outcrop. I don't think we can trust the leaked map for railway lines, there are several that don't match up perfectly.
(Like this fucking thing to the right of the horse's head, still no guess with that one. There's no three way rail junctions in that neck of the woods.)
I can only assume the line north of Mossy Flats joins up with the line east of Emerald Ranch in a different place to where it does on the map.