GCpedia is as secure as any internal government website, email or shared drive. GCpedia is running on Shared Services Canada production hardware that is backed up every day. TBS also regularly backs up the site. Pages are also protected from user deletion through the page history tab on the site. If someone deletes content or a page, the page history remains, which allows a user to bring up previous page versions. All edits on GCpedia are fully attributable to the editor.
Mediawiki software is designed to be open, and if a high level of access control is required it may not be the best solution. Problem edits are rarely an issue on GCpedia and that simply posting a notice asking others to refrain from editing the page usually works.
As a mass collaboration tool, GCpedia will never be a place for sensitive information.