Curb (TaxiMagic) is just a (bad) dispatch-management service; it's not really built into any taxi system, and doesn't provide any sort of feedback or quality control on the ride experience.
There is a feedback mechanism in Curb (I'm a former employee). For some taxi companies, LA for example, Curb has very deep links into the dispatch system and can choose not to offer rides to certain drivers directly - so enough bad feedback and the taxi driver will no longer get Curb ride offers. For other taxi companies reviews get reported back to the taxi management and they can act on the report as they choose (some companies act quickly and promptly and some others don't do anything).