I wonder about conditions for this plugin to work. I see it’s command line based, and it looks like it requires live database. Is this true?
I ask this as I wonder about the possibility of importing data that was exported from a database some time ago.
Yes this plugin requires to be run from command line, from a server that has access to both databases. Piwik must be configured on the first database. In other words, it lets you move data out of Piwik into another database.
A solution in your case may be (that’s just an idea) to import your data in a temporary database and set up a Piwik for that database. Then you can use the plugin to migrate the data from the temporary Piwik/temporary database into the real one.
Remember to backup your database before doing that!
import your data in a temporary database