Wouldn't say anything about "real," but in order for the plot to work, there had to be significant implied police corruption. They had to have their own cops, I think, in order to ensure that certain events happened promptly, causing other events to happen according to plan. (I'm trying to avoid spoilers; I think everyone can guess that there was a conspiracy.). Also, they had know somehow that a lady would be visiting HQ to get help about her husband.

On that note, the Godfather reference made me wonder if Mr. Big had his own cops. And, why is it that there were cops galore on the main plaza ready to chase a criminal, but once that criminal got to the rodents' part of town, there were no cops but Judy, who wasn't supposed to be there in the first place? Did the police leave protection up to Mr. Big?