I got 2 different answers to another question from the emabassy in DC. If I wrote in English, the answer was always "No". If I had someone write in Chinese, it was always "Yes, of course."
I've never heard of any Chinese embassy or consulate accepting items by fax, but if it's supplemental materials or corrections, they might or might not, or might say yes and mean no, or might say no and mean yes, etc., etc.