Multi Site Plugin Question

This plugin looks awesome as I have a new client who has a multi site. I have zero experience with multi site but need to setup test sites. This is the site: circles.com. The other sites are for France and Sweden. My worry is that this plugin will not work because they are on different domains completely. Does that matter or should the plugin work? I will lose the client if I break the site so wanted to check with you first. If you need access to be able to answer confidently just let me know.