Community Celebration Events are their own cache type so by default they don't count as regular events, just like Mega-Events don't. It's possible for a checker author to count them as events but this is something that is really up to the owner of the challenge cache to specify.
In this particular case, I'd say that the challenge doesn't specify exactly how cache types not listed (there are more) should be treated. In other places, the text talks about "non-traditional caches" and the CCE definitely is that, so it should at least count for that, even if it does not qualify as an event. Talk to the challenge owner and get a clarification. If that doesn't correspond to what the checker actually checks for, talk to the person listed as "tagged by" on the checker. Each checker is created by a volunteer, so they are not created by Project-GC itself.