Judging by Amtrak's own Track a Train map as well as the two unofficial tracking maps, No.7 of the 11th has just left Fargo on the Cutoff.
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www.amtrak.com]
Can't tell for sure yet whether No.8 that just left Minot is taking the Cutoff.
What's really interesting is the train ID for 7(11) is shown as 1007, and the late 8 and 28 that arrived Spokane this morning are shown as 1008 and 1028. Old timers like me will remember this is how BN ID'd the Empire Builder back when BN had its own trains that were numbered 7 and 8.
But look down south at this hour and you'll see that some of the Cal Zephyrs and SW Chiefs also show a 10 prefix added to their number.