This is a Wishlist item.

It would be VERY nice to be able to get evolution to automatically (or
nearly automatically) be able to import vcs files downloaded from the
internet. One of the places this is useful is www.salesforce.com, which
provides a link to a user to import the 'event' (i.e. appointment) into
outlook (by creating a v-cal file the user can download).

Under windows, clicking on this 'button' (aka link) brings up MS-Outlook
(if installed) and opens up the appointment for editing. 

I can't seem to get this to happen under Linux. It would be nice to be able
to associate the mime type (text/v-calendar IIRC) with evolution or
evolution-calendar or evolution-calendar-imported (or any other program)
which woul pop up a new appointment with the data from the vcs file.