Adding support for mCollective is currently a work in progress, primarily focused around the smart-proxy. There is a setting that can be set to true in order to use mCollective as the method to initialize agent runs from the host page's "Run Puppet" button.
All that needs to be done in order to enable mCollective support on the proxy is installing the puppet agent to each node where you'll need to run Foreman and install the required parts of the plugin on the server in order to initialize puppet runs. You can read about installing plugins on the Puppet Labs wiki page.
The proxy doesn't support the older puppetd plugin.