Hi Jose and thanks for getting in touch!
Good question. It would be possible to do that, but it’s a bit of a hack, admittedly.
For example, you could use our iCal Importer add-on to run a scheduled imports for those different sites, auto-categorize them, then set the Events Calendar PRO widget settings to display just those categorized events. You can have as many widgets on a page as you’d like, so you can embed as few or as many calendars as you’d like with the events from those sites.
Like I said, probably not exactly what you’re looking for, but it would be one way of doing it. 🙂
Let me know if you have any other questions and I’d be happy to help as best I can!
Cheers!
Geoff