Union Pacific UNP.N to buy smaller rival Norfolk Southern NSC.N in an $85 billion deal
NSC down 2.6%, UNP up 1.3% in premarket trading
Merger will create United States' first coast-to-coast freight rail operation
Combined enterprise value of co expected to be $250 bln, marking the largest-ever U.S. rail merger
Transaction could face numerous regulatory hurdles
"NSC is the belle of the ball," brokerage RBC quotes retired rail executive Tony Marquis
NSC reports Q2 profit rise
YTD, NSC up 22%, UNP up nearly 0.5%