I've heard that in the past, Columbia SEAS has contacted some applicants to their MSFE program who were not quite as competitive as those applicants to whom they did offer admission, and asked those candidates if they would like to be admitted to the MSOR program instead.
Similarly I've heard that Columbia GSAS has contacted some applicants to their MAFN program who didn't quite make the cut, and offered them admission to their MS Statistics program instead.
(I don't know whether or not this is still the current practice of each department.)
As albertino just mentioned, Engineering (SEAS) and Arts&Sciences (GSAS) are separate schools within Columbia University, each with separate (Graduate) admissions offices; you are allowed to submit separate applications to a single program within each school.
Similarly, Columbia Business School (CBS) is yet another school with its own, separate, admissions process; you could simultaneously submit a separate application for one of their programs, too.