Using Other Custom Post Types With Directory

I'm using an event plugin called Event Espresso for some, but not all, sites on a multisite install, and it creates post for a custom post type (espresso_event) for each event created.

I'm also setting up a directory on the main site for the same kind of event content, but want to include the custom posts from the other sites in the directory. Is there a way to have the Directory plugin include that custom post type even though it wasn't created by the Directory plugin?

Thanks,
ilana