Apple's Calendar reads a non standard property of the calendar file, X-WR-CALNAME, containing a calendar name that the importer will default to. However as far as I know this will only be set once per file. Like this:
BEGIN:VCALENDAR METHOD:PUBLISH VERSION:2.0 X-WR-CALNAME:Work PRODID:-//Apple Inc.//Mac OS X 10.9//EN X-APPLE-CALENDAR-COLOR:#711A76 ...
I created a new calendar for testing this, and created an event there,
exported that new calendar, erased the event from calendar, then imported the file and even that event is added to the default calendar.
I only see two ways here,
or I generate one ics file for each calendar and each time I import I change the default calendar,
or I add all to one calendar, then select by hand all events of same type then switch calendar type.
Seems harder finding out how to do it automatically
but if someone knows how to do it...will make my day
In my testing the calendar will be set to the calendar named in the .ics if the calendar exists in Calendar. If not it will list the default calendar and if you select the 'New Calendar' option it makes a new calednar with the title given.
You would have to make one file per calendar though.