It seems that an increasing number of institutions are making the decision to migrate from their existing Course Management System or Virtual Learning Environment (VLE) to Moodle.
The University of Strathclyde in the UK, with 29,000 students, is the latest institution to announce their decision.
According to Howard Ramsay, VLE Project Leader, "The University of Strathclyde University Management Committee considered the recommendations from the University’s Learning with Technologies Implementation Group and approved development of a Unified Virtual Learning Environment. Core to this will be the implementation of Moodle as the technical foundation for the Unified System. Full details can be found on the University’s website at http://www.strath.ac.uk/learningtechnologyreview/outcomes."
Further information about migrating to Moodle from other systems may be found in Moodle Docs - Migration.