The first two are quite similar, but they do do something with the concepts - the third, well if it was unused, you can hardly say he stole it, surely? And of course, therein lies the nature of this kind of thing - some of it might be appropriated, and some of it might just be coincidence.
Of course, Moore also has the Stephen King sentient cars thing in his future Shocks hall of shame too, as well as one of the Abelard Snazz's being a lift of something or other? I seem to recall that the intros to the old titan books had Moore addressing this very subject.