The default map used by Tableau is the OpenStreetMap, available here: OpenStreetMap
As far as I am aware, this map is continually being updated by the user base. A list of contributors can also be found here: Contributors - OpenStreetMap Wiki
Unfortunately I can't tell you much more than this on a city by city basis as this appears to vary by location. You can search the History section however to see recent updates (and even add your own I think): OpenStreetMap | Changesets
I hope this helps.