The music industry has the same problem. You can't copy a song note for note, but you can make music that sounds similar. Geez, there are only so many chord progressions you can do, the list is not endless. Remember when Geprge Harrison got sued for the song "My Sweet Lord" ? IMO, he got screwed on that one. There WAS some similar music to the song "He's So Fine", but note for note the song was different.
I would think the cue industry would be similar. If someone in Bumphuck, Egypt made a cue and someone in Kalamazoo made one that was very similar simply by coincidence, I would think as long as it wasn't entirely identical (which to get it accidentally identical would have to beat the odds in some form of a miracle) it wouldn't be infringement of one's copyright.
My personal opinion on matters like these is unless there is a blatant attempt to copy and market something that has a patent on it, there should be SOME leniency on those who make a product that is very similar.
Maniac