Just after the BN merger, and as conditions of the BN merger, the Milwaukee gained significant traffic from Portland and Tacoma (etc) to the point where they were running
5 trains a day each way on the Pacific Extension. Regulated rates at the time kept profit
margins slim and the MILW lacked capital to upgrade the Extension to meet the demand. MILW management at the time saw no end in sight to the problem and lost interest in the railroad aspect of the company and saw the railroad as a drain on the corporation as a whole and made
the fatal decision to form a holding company arrangement so that all the divisions of Chicago Milwaukee Corp had to swim on their own leaving the railroad under capitalized (much of the RR land went to Chicago Milw. so the railroad actually lost money it used to get from leases.) However, had deregulaton come about 3 to 5 years sooner, we would likely see the MILW lines west as a busy main line with it's more advanced construction and better grades (Saddle Mountains excepted) and shorter routing. Deregulation would have allowed better rates, easier plant rationalization and a new spark in the management that
most all railroads saw at the time. BN's interest in the MILW over the Cascaded came from a coal export project it had in the works about the time the MILW shut down and the management of BN at the time saw advantage to the better line over the mountains---just getting rid of Stampede Tunnel would have been huge. Both the NP and MILW lines run through water sheds that are protected, so that is a non-issue. Had BN kept both lines open, a badly needed double track line would now exist. But the Frisco merger forced BN to dispose of the MILW, the former Frisco management badly wanted to scrap Stampede too as they hated "line duplication" and even the former GN was eyed for elimination with the SP&S along the Columbia River viewed as the only line needed.