Ms. Koslyn's answer is correct for federal court cases in the District of Massachusetts; however, under MA Sup. Ct. R. 9A, which is a state court rule, the moving party must file the opposition with his or her Rule 9A package. It is the moving party's obligation unquestionably. File the whole package. Ms. Koslyn is correct in stating that you should not stress the late service if you chose to mention it.