Considering that the slide was not deployed, it is definitely unsuccessful. The MD-80 series (also the DC-9 and boeing 717) had tail cone assemblies which could be jettisioned in case of an emergency.
When operated, the tailcone is expected to swing to the left of the fuselage due to to its own weight because of the way it was rigged.
The jettison cone is attached to the slide through a lanyard, which passes through two eyelets in the tail cone and is attached to a spring in the middle of the cone.
As the jettison mechanism is activated, the tail cone is released and because of the way it is rigged, turns 90$^\circ$ and moves to the left of the aircraft to keep it from interfering with the slide deployment.
As it falls, it pulls on the slide container via the slide lanyard, moving it so that it can inflate and delpoy, while the tail cone remains to one side of the aircraft.
You can see it in the images below:
All images taken from Accident Report IN-045/2004
The following image shows the undeployed slide (in an MD-81) from the inside along with the lanyard.
Image from aircrewbuzz.blogspot.in
The release can be made by three ways- there is an emergency handle on the aft bulkhead door, one at the end of the catwalk and another one in the exterior of the handle.
In this case, the tail cone has pulled the lanyard, but the slide has failed to delpoy. While I'm not sure why the cone is hanging, it appears that the lanyard has snagged somwhere, probably in the cam rotator.
Note: This would not be the first time the slide has failed to deploy/deployed unsuccesfully or has deployed inadvertently. Also, see this discussion on the MD-88 tailcone jettison and slide deployment mechanism here.