Have the model files for the LEGO Sonic head piece been released in LDD or LDraw parts library?
I can answer half of this question. I have the latest version of LDD and after a thorough examination of the available head pieces, I can report that the Sonic mold has not been added to the parts library. If anyone else here has the latest LDraw parts library, they will be able to answer the other half of this question. 

Here is a shot of all the non-standard head molds: