Auto-assignment based on CI is
ONLY designed for R/I/P (Request\Incident\Problem) ticket types. See below screen print:
<Please see attached file for image>

For Change Orders this is not available, as you can attach multiple CI's to a Change Order which complicates the Auto Assignment algorithm somewhat.
<Please see attached file for image>

Please consider raising an Idea (Enhancement Request) via CA Communities for this to be voted for and possibly considered in future releases.