The brake failure during a maintenance test is an all too familiar story. I can readily think of incidents in the past with the 727 at ANC and EWR. And, of course, the infamous A340 incident at Toulouse.
CNN just had a live web page feed of the recovery efforts. The resolution was not that great but it appears a crew is attempting to secure lines to the landing gear to tow the plane back up onto the taxiway. A larger crew of supervisors is watching at the edge of the hill.