Just pulled out my handy-dandy '02 CAL Contract.

Part 3 Scope (C) The company will not directly or through an affiliate establish any new airline which operates aircraft other than small jets and small turboprops...

Part 2 Definitions (Y) "Small Jet" means jet aircraft with FAA certification of fifty (50) seats or fewer.

Part 2 Definitions (Z) "Small Turboprop" means turboprop aircraft with FAA certification of seventy-nine (79) or fewer seats.

Hence the reason CAL can put Q400's into EWR.