The Milwaukee Road's electrification - and really the entire Milwaukee Road Pacific Extension - was/is considered a novelty. Hence the enduring interest and "what if" speculation even though such scenarios are contrary to reality. How a railroad which could not even install CTC, power switches, lineside detectors, adequate sidings, or even continuous ABS on its main line could spring for new locomotives (and likely a whole new electrical distribution system) boggles the mind - even for the 650 or so miles under wire - which was not even continuous (that is, the "Gap" from Avery to Othello was never electrified). Of course those who fantasize about this will tell you they have crunched the numbers and it was totally doable.
Figures lie, and liars figure, of course, but there are constants in all the pro-electrification proposals: Ignoring the greatest costs, which are train delay, locomotive dwell, and restricting a large number of assets to a limited area of trackage. For electrification to work, the electrified network needs to be expansive and cover just about all the possible routes, or be a fixed single route usually with a single commodity. In the original posting by D.S. Lewith, he/she gives a link to a map of proposed electrification in the 1970s. Using the BN Powder River Basin to Lincoln, NE route as an example: During the height of coal movement it was not unusual to see 60 or more coal trains (loads and empties) on the route from Alliance to Lincoln. Today, most of these trains are 125 cars or more, and operate with distributed power. Just the thought of having to modify the entire locomotive consist of ALL the trains at Lincoln (from electric to diesel electric and vice versa) again boggles the mind. The amount of yard capacity to accommodate all the trains in the terminal would be huge, as would the locomotive fleet (of both types) to be kept on hand to be available to maintain fluidity. Plus, of course, the personnel to make all these power modifications. The cost is simply overwhelming. Same for the UP proposal with the electrification starting and ending at North Platte. 100 trains a day changing power? NOT. The Milwaukee Road would not have this volume of trains, but electrification still stranded a lot of locomotive assets on a very limited amount of track (Harlowton to Avery; Othello to Seattle/Tacoma). That meant power modifications for the "Gap" (or running the electric power through dead), and at the end or beginning of the electrification.
An additional explanation is here:
Milwaukee Road Pacific Extension: The myth of superiority
Here's another take on the costs of electrification proponents don't mention:
http://energyskeptic.com/2016/electrifi ... ight-rail/
With regard to NeueAmtrakCalifornia's statement, "then they could have sold the northern transcon (including the Pacific Extension) to Union Pacific, thus giving them a competing northern transcon to compete against BNSF": I'm sure UP would argue that they compete quite well with BNSF in this corridor right now, thank you. Not only that, compared to "transcontinental" routes to and from California, BNSF's route from Chicago to the Pacific Northwest has much more competition. Not only UP via Nampa, Green River, and North Platte, but also UP/CP via Eastport/Kingsgate. The port of Vancouver, BC handles more container traffic (and more tonnage overall) than does Seattle and Tacoma combined, and both CN and CP offer intermodal service from Vancouver to the Upper Midwest of the U.S. In addition, CN has service to middle of America from the burgeoning port at Prince Rupert, BC. But none of this matters, really, because even if there were not all those alternatives to BNSF, the Milwaukee wouldn't be around because the primary reason it's not around is that it was the high-cost route. The Milwaukee didn't electrify for no reason; it did so because its operating profile had horrendous grades. It also had a very poor and usually exceptionally circuitous branch line/feeder "network."
Milwaukee Road Pacific Extension: The myth of superiority
While proponents of the Milwaukee Road electrification and the Milwaukee Road Pacific Extension in general go to great lengths to explain why things turned out the way they didn't, it's easier to just focus on the operational deficiencies to easily grasp why things happened as they did.