It is not a formula like cross a Dark Cornish to a White Rock. It is geneticists analyzing the offspring of many controlled crosses over several generations, looking for the genetics that gives them the traits they want. It's not like you could steal a piece of paper or hack a computer and be breeding your own in a year or two. You would need to steal the eggs from the breeder flocks or the actual breeding birds that make up the breeding flocks. You probably could get some of the knowledge on how to feed and otherwise manage them to get them to grow as they do once you have the breeding flock. But then you would need the expertise to select which offspring would go back into your breeding flocks. It is not a one time thing, it's selecting the right ones every generation.
As R2elk said they don't want to help out their competitors though there is probably less secrecy than you'd expect. The real secret is the birds that have been developed in the breeding flocks. You can develop your own. Just hire experts in chicken genetics, chicken reproduction, chicken feeding, and many other aspects of chickens to develop the best management methods to produce these broilers. After several years and many millions of dollars you could be breeding your own. You might even get pretty close to as efficient as commercial companies.
