Batcache isn't an object and is still the array from batcache-config. Even though it's not running you can still clear urls if you replace $batcache->group with $batcache['group']. It would make sense to fallback to this
This causes a problem when you schedule a post, sometimes the slug is a 404 and cached for 24 hours, when the scheduled post event fires it will still be a 404 after publishing
The Batcache function clear_url( $url ) to clear cache for a single URL only clears the single page cache if the entire site cache has been cleared before using wp_cache flush.