The Windows 10 mail app also displays your calendar if youre configured for an Exchange server. Any idea if it's possible to add a subscribed calendar -- i.e. a shared calendar sent with a link like webcal://...? I sure don't find anything obvious in the "New Accounts" options or via internet search
I have been able to get an ical/webcal in after a few attempts:
All you need to do is add your calendars to your live mail account. Then remove and readd the account from your Windows 10 Calendar, and you will see them in there.
So it is not a direct method, but it works :)