I recently went through this process, because I have an older WinMobile 6.5 phone that used to sync to my company's Exchange server, but after leaving the company I needed to find a new way to sync my phone (calendar and contacts) to the cloud, and Google Sync didn't work for it. So I had to migrate my stuff to Windows Live.
What I found out: You can use Rainlendar to display a shared Windows Live web calendar on desktop, but you must use the web client, or the Windows Live Mail desktop client to edit the calendar entries. Rainlendar cannot be used to add and edit entries to your Windows Live account.
To make a Windows Live Mail calendar visible and available for Rainlendar, Share the calendar (thru the web client) and get the links to it, but don't specify any people to see it. You can then paste this link as a new web calendar in Rainlendar.
The only oddity I noticed is that it takes a few good seconds for Rainlendar to refresh the calendar, and if you change its settings, it seems to disappear for a while first.
Hope that helps.