The North American Numbering Plan Administrator (NANPA) amasses a list of assigned numbers from the providers twice-a-year and submits biannual reports to the FCC as the Numbering Resource Utilization Forecasting (NRUF).
Due to the sensitivity of this report, the FCC would never release or allow anybody to access it. However, with your suggestion, I suppose Cox could send a caller's number to the "database" and receive an "in-service" or "not in-service" response.
However, as you noted, scammers are spoofing in-service numbers, so the reply from the "database" would be "in-service" and then allowed.
You cannot rely on a company or agency to police your calls. The gov't has been failing for 20 years, and Cox does not want to get into the business of deciding which calls to block. The only foolproof way is to install a call-blocker and maintain it with an Allow Only list of numbers.