Hi John,
Thanks for contacting us!
Just to be clear, Event Aggregator isn’t actually a plugin as such – rather it’s a service that you can use from The Events Calendar once you purchase a license key.
That aside, yes – you can pull in data from a variety of sources. However, the websites you are importing from would need to supply the event list in a format that Event Aggregator can understand (typically, that means they need to supply the information using the standard iCal format): a plain text list is not currently supported.
Does that answer your question?