They will do this, if they are conscientious and detail-oriented, regardless of how the author and copyeditor have formatted the ellipses in the manuscript. The author is responsible for indicating the desired punctuation (an ellipsis), not for knowing composition conventions. The copyeditor, who probably ought to know something about composition but in many cases doesn't, should not get tied up in knots about whether there is a space before the …, after it, or both but should let the compositor take care of that detail.
I hasten to add that many books are produced by graphic designers who know less about composition best practices than most copyeditors. So practices have to be adjusted to circumstances. But in the ideal world, publishers would hire skilled compositors to set the type instead of relying on graphic designers.