I am an undergrad at UCLA. I went to the law school and asked about this topic, and they showed me the top feeder schools for UCLA Law, and they were the Ivies- Harvard, Princeton, Yale, and then really good schools like Georgetown, CAL, etc. However, UCLA was like third on that list, I think behind Harvard and Stanford. However, the admissions people told me in this case, do not let stats fool you. Indeed, a lot of schools with undergrads attached to law schools have similar stats, which makes it seem like the Law school favors the undergrad.
In UCLA's case, the admissions people said there are certain factors that make it such a big feeder. Number one is they get the MOST apps from UCLA students. Familiarity, not wanting to move, but mostly UCLA is HUGE with lots of students. These were all factors. Thus they said that while UCLA is a major feeder for UCLA, they give ABSOLUTELY no favor to UCLA students at all.