First off, the (high) majority of grain traffic in general generated on HESR lines both in The Thumb & Marlette makes its way out of MI via LS/CSX in Flint. Interchange would be in Saginaw.
The three lines which go to the thumb:
Ex C&O to Bad Axe and beyond is operated by HESR and enters LSRC at the yard.
Ex MC which is truncated short of I-75 still has a customer, which I believe is HESR, using LSRC Saginaw Sub for access.
Ex C&O to PH. This line is still LSRC to Nexteer (which occasionally has traffic), but is HESR beyond that. Same thing, HESR uses LSRC Saginaw Sub for interchange.
And it get's worse, out to Paines in LSRC, but then changes to HESR. But, HESR maintains the signals...too confusing to type.
Feel free to correct me, if I'm mistaken anywhere.