If you're absolutely dying to know, you COULD call and ask how their WL movement has been in recent years. They will usually be pretty honest if the WL hasn't moved much. I did that for one of my schools, which was also a UC, and they confirmed that in the past years, waitlist movement was minimal. They also gave me their input on things I could possibly do to help my chances (although small, and probably not super significant).
I remember
@gyngyn saying that CA schools are running a new algorithm in terms of targeting students to accept, and it has supposedly improved the yield dramatically. So that sucks
🙁 Sorry about that! Being WL at one of your top choices sucks! It's like going on a first date, thinking it went well, and then the person never calls you back.