As an aside - I was able to successfully import that webcal feed. The events inside it are in the past, however, so they may not show up immediately unless you go back and find them.
As Jim says, if that webcal export itself adds a new event, then the software should import it the next time it checks the feed at that URL. If the export itself is not updated, or a different URL is generated when a new export happens, then it will not be automatically added to the community, and would need to be added manually.