The Hausdorff Institute in Bonn periodically organizes thematic junior trimester programs, which "give young mathematicians (postdocs, junior faculty) the opportunity to carry out collaborative research" on a certain topic.
Are there similar programs in other institutes in Europe or around the world?
Fields Institute in Toronto has a similar programme that may be even older than the one you described. It is called Fields Undergraduate Summer Research Program (FUSRP) and is aimed at matching groups of talented undergrads with mentors at Fields during the summer and exposing them to serious research.