Does anyone use Craft CMS to set up an intranet for client? I heard that Wordpress has a BuddyPress plugin could set up as intranet which has shared files, shared calendars, chat .. etc feature. Does Craft CMS has any plugin to do a similar feature?
There currently isn't a single plugin that does everything that BuddyPress does.

There are calender plugins, commenting plugins, social login and oauth plugins and Craft Pro has built-in front-end registrations with member accounts with user groups and permissions. It would be up to you to tie all of these pieces together for your site's requirements.