UCs will not give duplicate credit for a college course and an AP score for an AP test covering substantially similar material. See the bottom of http://admission.universityofcalifornia.edu/counselors/exam-credit/ap-credits/index.html . So if you completed college courses that UC accepts for calculus courses for your major according to http://www.assist.org , AP calculus scores will not be of use to you.
The main advantage of taking the AP calculus test would be if you decide to attend a non-UC/CSU school that may not want to accept the college course for subject credit but does accept AP scores (e.g. University of Michigan engineering is reportedly stingy with allowing students to take advanced placement in math from college calculus courses taken while in high school).