I stumbled on this solution by accident while I was trying to get an ical from my boss to sync with google so that I could sync it on my Lumia 1520 via google calendar (which doesn't work as well as this solution does.
Here is what has been working for me:
Copy the webcal share link (webcal://p04-calendarws.icloud.com/ca/subscribe/
Go to https://icaltogcal.com/
Use the site to generate a new URL
copy the new URL
Log into your Microsoft Account that is associated with the phone you are using.
Go to the Calendar tab
Click IMPORT (between New & share)
Next page choose the SUBSCRIBE option
Paste the new calendar URL you got from https://icaltogcal.com/
Go to your Phone Settings>Email+accounts
Sync your Microsoft Account
Your new calendar will instantly appear on your phone.
Sync time is immediate. when my boss updates his shared calendar, my outlook.com, and phone calendar update within minutes.