From my observations, there is no automatic reopening.
However, I've only seen this happen when one person keeps asking the same question over and over (usually in frustration over not getting any answers to the first version). In that case, the later versions are sometimes closed as duplicates. They are not automatically reopened when the first is self-deleted (nor should they, as this type of behaviour should not be encouraged).
I should add that in the case of similar questions asked by two different persons, this is very unlikely to happen.
The rules for self-deletion are:
Users can delete their own questions if the question:
- has zero answers
- only one answer, but that answer has no upvotes
And unless POST-B has at least one upvoted answer, it is very unlikely that POST A will be marked as a duplicate of it (posts are not marked as a duplicate unless the superior question pointed to has a usable answer).
If POST-B has at least one upvoted answer, it can't be self-deleted, so the situation will not occur.