>It seems that to be truly be effective in rat reduction at a city scale the fix may need to come from elsewhere and may have very little to do with directly working on exterminating the rats

yeah, basically treat the root cause rather than symptoms of the problem. Hiring more rat killers is like taking pain killers instead of fixing whatever injury is causing the pain.

Realistically this problem would require some sort of position that has temporary authority across multiple departments where systematic changes need to be made to actually solve the problem. Instead you get more rat killers as a band aid solution