South Korea, Taiwan and Singapore all had significantly lower crime rates before CCTVs were all over the public space.

EDIT: also, most crime happens at home, so if you really want a large reduction put cameras in everyone's home too.

Singapore is very diverse racially… with groups that aren’t generally known to be very criminal. It’s mostly a mix of Chinese, Malays and Indians. I doubt the CCTVs have much to do with it.