Based on the presentation by EASA at the March 13, 2014 (ie 1 month ago) open session (see my previous link) it does NOT appear that the Cessna SID programme is mandatory.
It is clear that EASA WILL make some parts of the SID mandatory for some aircraft in the future. But as I read it they are still deciding what to do. See presentation 4b, slide 8. And remember that this powerpoint was delivered by EASA itself.
Both EASA and the FAA in presentations acknowledge that they do not have data or have not analysed data they do have in order to understand which elements of the Cessna SID are important in the real world.
So, the question remains. Why has CASA made all elements the Cessna SID (which was written with the intent of being an optional programme) mandatory for all aircraft in all classes of operation by prescribed deadlines?