Sanofi has to show that their process is reasonably the same as that which was approved. There is no reason to assume they have to be able to characterize Lovenox to any substantial degree. Furthermore, I seriously doubt they did characterize to anywhere near the degree the FDA now expects.
A generic can not possibly match the S-A process, so they have the much harder path of proving the output is the same.
EDIT: If somebody wants to run trials and create a branded generic then that could easily be done w/o infringing.