I have just completed a Joomla intranet project. Two district councils are embarking upon a programme of “shared services” in an attempt to reduce costs and improve efficiencies.
As part of this programme, these district councils are to share a common intranet, removing the need to renew licences for a propriety content management system. This was part of the reasoning behind the choice of Joomla! to power the intranet. Another reason they chose Joomla! was the belief it would be cheaper than Drupal!