Hey there, and thanks for reaching out!
Great question. If you’re able to contain all of your event in CSV format, then The Events Calendar has a way to import everything in at once by uploading the file. That’s by far the easiest way, if it’s available to you.
We also have iCal Importer, which will import events from another calendar that has either an ICS file or feed to pull from. That would be another way to go about it. This will soon be replaced by a new product called Event Aggregator, but will certainly get you through the migration process in the meantime.
But to directly answer your question, it is certainly possible to migrate one site database into another — but I do think that would take a consider amount of work to ensure that all the database tables are matched accordingly.
Does this help answer your question? Please let me know. 🙂
Cheers!
Geoff