They were, however, "consulted to ensure accuracies within the fiction"
Treyarch has said that they haven't been involved with the development of PlayStation Vita shooter Call of Duty: Black Ops Declassified.
Communications manager John Rafacz stated that Treyarch nor Modern Warfare developer Infinity Ward have been involved with the shooter's handheld version.
While they're not involved with the shooter in general, Activision did confirm that due to Declassified's story having a timeline between the original Black Ops and Black Ops 2, Treyarch had been "consulted to ensure accuracies within the fiction".
Call of Duty Black Ops: Declassified is currently in development by California-based Nihilistic, but with Sony publicizing the game more than Activision itself, you wouldn't be wrong in assuming that the former may have picked up the game's publishing rights. However, Activision clarified the matter by stating:
"Activision is the publisher, but we also have a partnership with Sony to bundle Declassified with the PlayStation Vita."
Call of Duty: Black Ops Declassified is due for a release sometime during November, 2012.