I believe I can answer that with a yes. My wizard Tath started out as a generalist and after having some good RP with some evil people and being an apprentice to a necromancer has become a full necromancer, I have asked to be changed to a Necromancy specialist however since going from an Evoker Specialist to Generalist, or Generalist to Specialist both have their pluses you either need to have done some very good role playing (and most likely kept a detailed journal for your character) or yeah, do a CDQ to fully reflect the change you wish to persue. However I'm not sure if my wizard will ever actually get the change to Necromancy Specialist LETOed in, it may be something that L and the 'Big Dawgs' just want to keep off the market for now.
ZV-