Hello Sapling and thanks for getting in touch!
It is definitely possible to upload an .ics file into The Events Calendar and use that import events from your other calendar.
Our iCal Importer add-on does exactly that. you can upload an .ics file to it, or enter in the URL of a valid and hosted .ics file and it can schedule events to import automatically.
Does that sound like what you’re looking for? Please let me know if you have any other questions and I’d be happy to help.
Cheers!
Geoff