In my 58 years I've seen the number of "Class I" rail carriers in the US and Canada dwindle from about 120 to perhaps 15-20, and only seven of those could be characterized as major players. The more pro-business attitude in Washington in the years following 1980 is sometimes credited for this, but the "merger movement" can be traced much further back, at least to the days of the Truman administration. And the pressures that forced that "solution" began to mitigate around 1985.
Furthermore, technology and entrepreneurship has been (admittedly slowly) eroding the narrow definition of a rail carrier. The remaining majors will certainly fight any attempt to open their lines to all comers, but the nessage that some sort of major rebuiild of our entire rail system is necessary to deal with a fossil-fuel/mobility crunch that is just getting started seems more credible every day. That, in turn, could force some compromises, with the prospect of Federal participation used as an incentive. You might also see an entrepreneur attempt to knit a couple of shortlines/regionals in relatively flat country together.
Here are links to two tantalizing scenarioes:
http://www.railroad.net/forums/viewtopic.php?t=44412
http://www.railroad.net/forums/viewtopi ... c&start=30
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It's going to get very interesting; gives me one more reason to want to live to be a wise old geezer.