There are some past mergers that made sense.
Yes like the Penn Central!
Try two years later: The Burlington Northern!!!
The BNSF has been a winner too.
The N&W, Nickel Plate and Wabash merger was successful as was the later N&W - Southern merger.
The SP-Rio Grand merger went well in its brief history.
UP did well with the WP, MP and Katy mergers.
The UP blew up their railroad for some months by mishandling traffic after their merger with the SP but the SP on it's own would likely not have had the cash to start double tracking the sunset route. There is a real need now for that extra capacity.
And since their merger the BNSF has made major improvements in Abo canyon and on Stampede Pass.
The problem with the PC merger was that the P was poison and the C was no antidote.
PRR+N&W and C&O+NYC would have been natural. It only took the nation's largest corporate bankruptcy and 40 years before nature was allowed to assert itself and give us today's CSX and NS.
CP+CSX might be Hunter Harrison dreaming out loud. But CP+CSX+UP and BNSF+CN+NS would be a reasonable end point for North American railroading. The conditions of approval could fix some of the problem areas that have impaired competition today. In my corner of the country granting UP trackage rights over Stampede Pass and access to the Montana Rail Link at Spokane would improve competition. Requiring the BNSF to sell the UP the former MILW from Miles City, Montana to the twin cities and sell the UP the segment of the former NP covered by the MRL lease would be better still. Better access for the UP in the northwest could be evened out by requiring the UP to sell the former WP and Rio Grand to the BNSF to provide better competition from Denver to the San Francisco Bay area.
If CP+CSX+UP ever happens what are the odds they will name the new railroad by using the CP's last name and the UP's first name?
No, the CSX won't get any part of the new name.
But the KCS will get Mexico.
Viva Kansas Ciudad Sur!