You would need to ask someone who has done that...both are nice breeds, but that cross won't give you a California Grey/Gray (I'm still unclear on the spelling) directly.
Developing the breed was a multigenerational effort begun by James Dryden who was a poultry scientist at what is now Oregon State. He developed the first 300 egg hen and utilized some crossing (which was apparently borderline breeding heresy and I saw a reference to threats to pull his funding). But he was after a good farm bird and production, not 'fluff and feathers' and breed standard looks). He even made it into the US Agricultural Hall of Fame for his work.
Once he left the University he ended up in California where he continued his work. He died in 1935 and his son Horace ended up selling the breed commercially into the 1940s at least. I'm still looking for some of the old sales listings from their farm in Modesto.
In any case the Drydens did the work to produce a breed, not a cross or hybrid, that happens to be derived from Barred Rocks and White Leghorns. But, they are a barred breed that lays white eggs, not a hybrid.
You might be thinking of the California White which IS a hybrid. Apparently that is the California Grey rooster with a White Leghorn Hen. You get a white bird with a few black specks, that is a truly prolific layer of white eggs.