Because nobody knows exactly how Copaxone works, there is nothing that corresponds to the enox measurement of anticoagulant activity which was part of the FDA enox "sameness" criteria. Thus there is no preclinical test that could be done to show that M-Copax has the same effect as T-Copax.
When Teva got Copaxone approved, of course they had to run preclinical safety tests and then go through the normal clinical trial process. But the whole point of a generic is to avoid having to repeat those trials.
I really have no idea what the FDA thinking will be in the case of Copaxone. But enox is not a complete analogy - in my view Copaxone is harder. In one sense harder is good - means MNTA wouldn't be faced with an overhang from another prospective entrant; but of course harder is initially bad in terms of getting approval in the first place.