You can set a calendar shared with your Google Calendar as the sync source when setting up a new sync policy:
Navigate to the Calendar Sync page in Reclaim
Click the + New Sync button at the bottom of the page.
Under the 'Sync from' section, click the downward arrow next to the box showing only your email address to see a list of your shared calendars associated with your Google account.
Select the shared calendar you want to sync.
Click Next: Preferences.
Customize your syncing details.
Click Start Syncing to complete setup.
Learn more about the differences between a Primary and shared calendar.