could be line-breaks a problem?
I don’t know about how OwnCloud handles line breaks. They’re at least correct and all clients I know can correctly handle them. But OwnCloud people could surely answer that.
With DAVdroid 1.8, it’s now possible to subscribe to/unsubscribe from CalDAV-advertised Webcal feeds (“subscribed calendars”) by integrating ICSdroid.
ICSdroid is a separate app for synchronizing Webcal feeds and can now be used together with DAVdroid (but also as a standalone app).
New in 1.8.1:
Better support for read-only address books: