I'm not sure that this is accurate. There was a case in New Jersey a few years ago that ended up going to the Supreme Court. I can't find the link to the story but here is basically what happened. A police chopper on a random fly-by spotted a heat signature coming from the man's house. They then used this as probably cause to get a search warrant. They did the search and found plants. The judge ruled that the search was illegal b/c the evidence they used, took away his right to privacy in his home.well your biggest problem is the heat signature given off by all the heat buildup. If a police chopper does a fly bye and sees that heat, your done for!
(remember that the police scanner can only pick up the heat signature directly on the surface of objects) So if you run cooling pipes on the ceiling you can remove that risk.
This is not to say that a heat signature can't get you busted. Now cops can spot your heat signature and use that as a flag to follow you, watch you, look through your trash, etc. This means if you are very discrete about your grow (disposing of trash at another location, etc ) I don't think you could get busted for the heat signature alone.