AFAIK the first experiment was ClickTracking for the usability initiative in 2009-10: https://www.mediawiki.org/wiki/Extension:ClickTracking https://usability.wikimedia.org/wiki/ClickTracking We've waited for its data for years, I suppose we can assume it will never be shared; it had some anonymization problems (aka nobody bothered to check if there was something non-anonymized in it). It was used only to decide that collapsing everything (even interlanguage links) on the sidebar was a good idea: https://usability.wikimedia.org/wiki/Opinion_Language_Links That's history.

In the current status of things, all such tracking features current and future are – I believe – supposed to use https://wikitech.wikimedia.org/wiki/EventLogging (this page is outdated). In a bright future, all such data will be available for everyone via https://www.mediawiki.org/wiki/Kraken , so I think that in this non-mythological present nobody will bother to do work that would end duplicating those features and only WMF people will have access to it. If something happened to be available, you'd most likely find it on http://datahub.io/en/group/wikimedia (there doesn't seem to be anything).

Nemo