Looks like Google Calendar can import your iCal of Tracker, but Windows Live chokes with "This calendar wasn't updated because of a problem with the publisher's file. We'll try updating it again later." Any idea why MSFT doesn't like your format? Thanks!
Sorry for the frustrations. We've heard about similar problems with calendar subscriptions, and have not, at this point, been able to fix the issue. We'll be removing this feature in the near future, but hope to have an improved version we can include at a later date.