It's a fair question, one I'm not sure I can answer clearly. I'm not particularly familiar with Saint-Saens's other work- I know his Danse Macabre reasonably well, and have a casual acquaintance with some of his chamber work. More pertinently, I've seen several different visual adaptations of the Carnival over the years, including some with added narration, and am presently uncertain if I saw one of the visual adaptations first or if I first heard the music on its own. Probably I heard the music first on its own, but unquestionably those visual adaptations play a role in how I imagine the Carnival when I hear it.

On the other hand, I'm not sure how important that is. When I hear REM's "Nightswimming" (cited as an example for no other reason than that I heard it last week and was struck with memories), I access a whole web of associations and memories from when I first heard the song- people, places, events. If I requested "Nighswimming", I obviously wouldn't be asking my writer to consider that web of associations.

I think ultimately it doesn't matter what other context I bring to the Carnival, just the context that comes directly from the 'scenario', which probably in the end means whatever context wikipedia can provide. In contemplating it, "Is there sufficient information on the song's narrative on Wikipedia?" is probably a reasonable heuristic to apply for in/out of Jukebox.