In regard to the Edgeworth matches: When ERR was discontinued, Sutliff's master blender Carl McAllister recreated it, and in my opinion, was very successful The only real difference I note is the original had a little deeper molasses flavor. I'd say it's 95% of what the original was.
In the case of Lane, they are using the original formula, but it doesn't taste quite the same. The cut of the tobacco is a little different, and there's a little more cocoa taste than molasses, whereas the original and Sutliff match flavor had/have less cocoa than molasses. Why is it different? Lane uses different sources for the tobaccos and the flavorings, the latter accounting for the difference in the ratio of cocoa to molasses.
So, even if a company has the recipes for the Dunhill blends, if they don't use the same sources, the blends will not be 100% accurate.