Here are 2 interesting links about this:

http://connect.educause.edu/Library/EDUCAUSE+Quarterly/IfYouBuildItTheyWillCome/39950

Here is a comprehensive presentation on the UW implementation. It gives you the background information on University of Wisconsin and the project. It should answer many of your questions as well as provide you with additional information. Most of the integration work was done by the staff at UW. Xythos gave direction on the architecture as we do in most cases, but they have a pretty significant IT staff. These links may be helpful as well.
 
connect.educause.edu/Library/EDUCAUSE+Quarterly/IfYouBuildItTheyWillCome/39950

connect.educause.edu/Library/Abstract/UbiquitousSecureDocumentS/41408

connect.educause.edu/Library/Abstract/UniversityofWisconsinMilw/41959

 

 

Uportal is very central and probably the leader portal for the education sector.

The University of Wisconsin has integrated Xythos with Uportal, like many other universities: 170+ in USA and more than 40 in FR

THose FR universities are listed on one wepage of Uportal
http://www.esup-portail.org/pages/viewpage.action?pageId=2064438

and here is the site of the FR Uportal community.
www.esup-portail.org/display/ESUP/Bienvenue+sur+le+site+du+consortium+ESUP-Portail+!