This can be partially tracked, but I do not think we have access to this data.
The Hot Network Questions link URLs don't currently include a tracking parameter. However, there is the HTTP
Referer header which can track this for the most part. There are some limitations on using the
Referer header only:
If a hot question is visited from a different site, during the period it was on Hot Network Questions, then they can be reasonably sure that it accessed was via the Hot Network Questions list.
You know it was not via the Featured Question Ads because those do have a tracking parameter.
Unfortunately, Stack Exchange could not readily distinguish a user link to a different site, vs a Hot Network Questions link.
For example, if you click this here: How does an attacker get access to hashed passwords?
Stack Exchange cannot tell whether it was from the link I just gave you, or the Hot Network Questions on the right column.
If you are viewing Stack Exchange in
https mode, then, because the Hot Network Questions are still
http links (they should fix this one day), the
Referer would be stripped during navigation from an
Same-site tracking just doesn't work. User links in the same site are much more common and I can find the same question either by search, or in this case, on the home page:
So in summary, they just can't track this for same-site navigation. With cross-site navigation they can track these with reasonable accuracy, but not 100%.
I wonder why they have not added a tracking identifier to the URL? You would think it would be useful data for them to have, even if just for internal purposes. :-)