"Maintenance of way" work . . . complete sections of right-of-way are taken off-line, for routine grading, tie replacement, etc. If the parade of tie cranes, tampers, ballast regulators, and related equipment can have access to a line for a day or so, they can efficiently improve miles and miles of track. But if they constantly have to stop and put equipment on a siding for every passing train, it can take forever.
It sounds like MOW crews had full access to the CNO&TP line, with scheduled trains re-routed elsewhere.