in the big scheme of things police do have alot on their plates, murders etc. not trying to get up anyone, but just something to think about, from their point of view a stolen car is a stolen car, regardless of if its a $500 corolla or $40k gtr, that, and they are pretty badly understaffed.
having said that, yes it does take ages for them to do something, but sometimes they are quick, they arent consistent, thats the problem.
anyway, i think the bait idea is awesome and could actually work, for small time crooks, but if your trying to fight a car theft syndicate like adelaide has been known to have then i really dont think its worth the risk of meeting someone in the dark with weapons they arent afraid to use.