UC Berkeley’s Institute for Governmental Studies has published this research study. From the press release:

Redistricting reform could increase the competitiveness of some California Congressional and legislative districts, according to a new study released today by the Institute of Governmental Studies at the University of California, Berkeley.
After drawing dozens of potential redistricting plans, researchers concluded that attempting to create more competitive seats while also balancing other criteria would probably produce 12 to 14 competitive Congressional districts and 12 to 17 competitive Assembly seats. Currently the state has no Congressional districts and five Assembly districts that fall within the study’s definition of a competitive range. Increased competitiveness has been one of the outcomes sought by those aiming to take the process of redrawing legislative districts out of the hands of the Legislature.
The study cautions, however, that while such districts would be closely divided along partisan lines, they would not necessarily produce frequent partisan turnover. Factors such as incumbency, monetary advantages, national political trends, and candidate quality make it unlikely that closely divided districts would ensure a sharp increase in the frequency with which seats change hands, researchers found.
The ability of any redistricting plan to create a high rate of partisan turnover is “greatly limited,” the researchers wrote.