It's complicated, and not public. Here are the rules I've deduced.
If you submit the exact same link, or a link that is sufficiently similar under some rules that are not made public (and hence I don't know), and if the previous submission is sufficiently recent, or in the cache for some reason, then yes, your "submission" will act as an upvote on the previous link, and you will be taken to it.
However, if:
* The link is not exactly the same, or
* the link is not "nearly the same", or
* the previous submission is not in the cache, then
your submission will be accepted.
