Based on very few data points, i.e. colleagues’s children’s experience at UC’s. One girl transferred from some biology like major to bioengineering (in engineering) in UC Davis about 3 years ago. One boy transferred from a math major to CS at UC Santa Cruz, which was about 6 years ago. I haven’t heard of a real case transferring into engineering at UCLA. They won’t say it’s not allowed but must be really hard, especially if wanting to transfer into CS. I will ask around.