Here's our experience...

We had three separate knowledge bases: 1. Public - available to all employees 2. After Hours Support - available to our vendored after-hours service desk 3. IT Only - only visible to our IT department

This was problematic in that those that were writing articles were not sure which KB to use. It also led to lots of duplicate information for issues that had a self-service component but if that doesn't work then here's what after-hours can do and then what IT can ultimately do to fix the same issue.

We switched to using the already existing Public KB and building a template (we follow KCS methodology so we started with that OOB template) and added fields for After Hours Resolution, After Hours Escalation, IT Resolution, and IT Escalation. We applied ACLs to those fields and used group membership to allow access via the ACLs. So, the entire article is visible to IT. After Hours vendor can only see the Public fields and the After Hours fields. All employees can only see the Public fields (Issue, Cause, and Self-Service Resolution).

We just started down this path earlier this year but so far it's been working out very well.

The only drawback so far has been having to rewrite/recreate an existing article using the new template and abandoning (retiring) the prior article. ServiceNow does not have a way to move an existing article from one template to another. We have been putting the previous article number in meta so that if the previous article number is out there, someone will find it by searching. However, any permalinks that might have been shared for those articles will not lead you to the new one.

We are US based and only write articles in English.