Sun's CDDL is based on Mozilla's MPL, and is expectedly incompatible with GPL.
What about the MPL itself? Is the CDDL compatible with the MPL?
For new projects, you should avoid the MPL as it has issues with the European law system. For this reason, the CDDL can be seen as the sucsessor of the MPL.
Given that both licenses disallow to change the license but limit their scopt to files, you are still allowed to combine files under different licenses to make them together compile a single work.