This is definitely an Obama flip-flop, but it's a good flip-flop. Doing this will lower transportation costs, which will increase business profits, which will allow businesses to hire workers in other areas. Also, lower transportation costs will increase real wages on the whole (due to lower prices of consumer goods).
BTW, this is a perfect example of why NAFTA isn't really free trade, but managed trade. THAT is the real reason why we need to get rid of NAFTA.