Are you sure the distributors don't already know about the other brand?
The way I read the post: The distributors know exactly what's going on. They just don't want the consumer to know, for fear they'll sneak off and do their shopping at contractors' outlets instead of in retail stores. So neither brand can even hint at the existence of the other brand.
Wouldn't rel="canonical" be kinda disastrously counter-productive because it just highlights the fact that the two products are really the same?