It looks like the Calendar/Dates modules don't add Views Display types directly. Instead you're apparently supposed to copy one of the default views that come with Calendar to access the additional displays. However, the default views are Node views and I want to create a view of non-nodes. For example, say I want to create an iCal feed display type listing the dates users created their accounts on the site. Is there a way to do that using the Calendar/Date modules?
I made several attempts to use the iCal functionality included with the Calendar module, but in the end I gave up on that idea. Instead, found an issue associated with the Views Bonus Pack, with code for adding iCal support to that module.
I made some modifications to allow me to use arbitrary Views fields in an iCal feed. I'm interested in hearing feedback on the idea, if anyone here gets a chance to try it out.