I've imported ics files into other programs but not TB. And yes, if I
import into Google calendar online or my Rainlender2 desktop
application, I usually make a new empty.
I'm never sure as there was one program once that would only import as
it made the calendar (Google I think). I used to use Desktop icalendar
Lite
http://www.desksware.com/desktop-icalendar-lite.htm and so between
4 imports, I never know which is going to do which.
But it doesn't matter since the ics from TB is a full calendar and if an
import DID dupe, then you just clear it and re-import.
I have TB linked to google calendar via the 'provider for google
calendar' extension in read only mode. And I use Rainlendar2 desktop
app to edit events, and it updates Google and then TB updates from
Google. Or I update google from my phone and both TB and Rainlendar2
update from Google. Sounds like a mess but it keeps everyone happy.
My wife runs Rainlendar2 from here PC and uses my google login to access
the calendars. So we both make edits and we both get the events. It's
pretty neat once I got it all put together. She's on Windows and I'm
on Linux and it still works. WooHoo. LOL
I import Nascar calendars every year and I have to edit the ICS file and
do search and replace and modify data. There is a description and a
comment field and they seem to put data in the wrong field for it to
show on my Rainlendar2 desktop right. So I flip fields.
I know... TL;DR But have fun!