CSX has a $62.5 billion market capitalization, compared to $58.7 billion for Norfolk Southern. Union Pacific is the largest of the three S&P 500 railroad stocks, with a $138.1 billion market cap. BofA also cited CSX's internal improvements in the upgrade, according to The Fly investment site.

Stagnant volumes that have shifted to the trucking sector over the years appear to support the arguments for railroad consolidation.

Combining Union Pacific and Norfolk Southern into the first transcontinental railroad in the U.S. would create a 52,215-mile colossus that could offer seamless service from coast to coast, bypassing longtime interchange choke points in Chicago and at gateways along the Mississippi River.