Assuming the Class 1's are doing supertrains too (ass.u.me but in the present environment it's a pretty safe one) ... could they be contributing to some of the chronic black holes for Amtrak long-distance schedules? These are spots where Amtrak's alerts usually blame a significant delay on "freight train congestion" or "rail congestion" (on a line where the daily or triweekly Amtrak is the only passenger train) or "disabled freight train." Some that crop up almost daily include:

BNSF just east of Spokane, between Flagstaff and Gallup, and between Newton and KC.

UP (snide commenters would say "almost everywhere" but some are more common than others) just west and north of San Antonio, and between Elko and SLC.