The process of finding out whether the Rules are being implemented must start at the national level. Rule 20 sets out the basis for national monitoring.
First, it says that there should be regular, systematic evaluations of national disability programs, the results of which should be publicly disseminated. The evaluations should follow criteria for sound processes, starting with a baseline and comparing changes against the baseline. It should be built into the programs and be developed in cooperation with the organizations of persons with disability.
To be successful, criteria should be developed that allows for evaluation. This means determining indicators of both results did the programs improve the lives of persons with disabilities and process were the programs efficient and participative. These criteria should draw on international standards and the national monitoring mechanism should participate in the development of these international standards.
The fact that this rule was almost never implemented tells you how difficult monitoring could be. Should there be a convention, it is likely that an international body would be set up to which States would report. They would establish the criteria that governments would use.