Quite possibly the reverse was done: machining the Delta Elite slide to fit over the .45 ejector. However, I suspect there might be ejection problems. In either case, only a small thickness of metal would need to be removed from the slides to pass by the mismatched ejector. Perhaps given favorable tolerance stackups, you might even find examples that would slip past each other.
However, I can assure you that in previous attempts, my .45 Government Model slide will not slide past the ejector on my Delta Elite frame, nor will my Delta Elite slide fit past the ejector on my Government Model frame.