I don't see why it could not be possible that in some variation of the universe the Chronoverse and its own variations exist.
The problem with saying that fiction exists in other univereses, however, is the simple fact that in many cases the universes operate with completely different physics, rules of temporal travel, and so on and so forth. Now, admittedly, this isn't actually as much of a problem as it might seems, since alternate universes can develop their own laws of physics, but it would be very dicy, especially given how many of those universes involve groups of other alternate universes. Sliders alone would possess at least 1000 universes all by itself.
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Of course, since there are supposedly an infinite number of universes that number is startlingly irrelevant, but it's things like that which would make locating other universes very difficult, and the simple fact is that in this universe it may not be possible to develop technologies to traverse the universal barriers, presuming that they do indeed exist, since they really haven't been fully proven yet. Even if we could, finding the Chronoverse would be like looking for a needle the size of an atom in a haystack the size of the universe, which is probably not even close to the actual scale, since we'd have to find the specific planet in that universe, determine that it is the version of the Chronoverse we want, and so on and so forth...it'd be nuts.
So, all in all, it's, at most, an academic discussion, albiet quite the interesting one.