Dictating isn't collaborating, though. Those are completely different things, because the transcriber doesn't contribute anything creatively, just converts the writer's words to text.
Sure, but there will also be degrees in how much the transcriber might be asked to contribute. Punctuation, corrections to the narrator's grammar, perhaps even a first edit, marking sections that seem to need expansion, or places where the narrative strays.
In any case, after Shatner gets back his transcript and fiddles with it, he passes it on to another writer(s).