It all dates back to when CSX sold the Port Huron Sub to Rail America in the late 90s. RA would have only handled traffic from Steering Gear for a only a couple miles into Saginaw Yard and gave it back to CSX. LSRC ended up with that traffic after CSX bailed out of Saginaw. Both HESR and LSRC run on the same trackage all over Saginaw because of how everyone in Jacksonville split everything off over the years.
HESR will run grain traffic out of Saginaw Yard on this line if its going toward Gera and Vassar, with most of the manifest traffic going out toward Reese on the Bad Axe Sub.