I can't say that our system is anything like yours, but hopefully this will help by showing you another perspective. Only our Site and one manufacturing building down the road are covered under our registration. We use a "canned" software package (IBS / QSI System 9000A / System 14000 Integrated) at my facility which helps us with compliance to the ISO-9001 / 16949 / 14000 requirements (though we are not yet registered to 16949 nor 14000), and helps us centralize, manage and control a lot of information in a few locations.
To document continuous improvements, we review the efforts of all our Departments at our Management Review meetings. Improvement efforts as well as measures against our goals and objectives, and any resulting Actions... these efforts are recorded in our Management Review database (MR meeting minutes and Actions).
Other continuous improvement efforts are recorded in our Change Management and Preventive Actions databases.
As for suggestions? with 20 managers at 20 locations, you may want to have a central system that each of those 20 managers can enter their notes in... Either make it easier for these individuals to provide you with information, or find the information elsewhere? Are they not providing you with information because they don't understand why you need to have it? If so, further explaination / training may help to get that information flowing? Periodically, we provide our Leadership Team with a full day or two of training on the ISO-9000 Standards. We typically see more cooperation as a result of that training.
One last thing which may ensure they would update their logs / notes would depend on who the boss is?
have you / can you make it part of their jobs to provide you with that information? are their raises / reviews conditional on how well they communicated their logs / notes? When faced with that brick wall - if all else fails, I either go above the wall or around it...