I would personally go about that by writing code on the central site that pulls in the data from the RSS feeds for events on each of the sub-sites; this is something we cannot help you with, but there may also be “RSS Import”-style plugins that do this for you. As long as they work with custom post types so that they can work with “events”, this would work well in my personal opinion.
We unfortunately don’t have any Knowledgebase articles about this.
With all this in mind, I will close up this thread for now. Best of luck with your project and any customizations you might make in relation to it!
Cheers,
George