Ability to add/modify filters for OG Calendar view

Issue Summary

I'd like to customize the OG Calendar view but it doesn't seem to be accessible via the Views module. Specifically, I'd like to add a filter by group for the calendar so I can show one or more group's calendar instead of showing them all. I can simulate this using a vocabulary that has terms corresponding to the different groups I have but this is less than satisfactory as it involves making sure to specify the correct term when creating the calendar entry and maintaing the vocabulary.

Any solutions?