In the world of auto-plant construction, that's quick. Building and launching a greenfield plant typically takes twice that long. And that's after months of site selection and consulting work.

FCA's fast-moving plan is a reminder that mothballed plants might well be a financial liability, in addition to a towering public reminder of past failures. But they can also enable an automaker to chop months or years off the timetable to add capacity and seize on a market opportunity.

It's a competitive advantage that's mainly available to the Detroit 3, which closed multiple plants during the Great Recession.

Bernard Swiecki, director of the Automotive Communities Partnership at the Center for Automotive Research in Ann Arbor, Mich., said an automaker such as FCA has several advantages in reviving its own brownfield site: "In this case, it's all within the same automaker, which does make it easier because you're starting with the ownership of most of the land."