BBC News - Scores assemble at atheist church
I've often thought atheism is really a form of faith. You cannot prove there isn't a god (or gods) so you have to have faith that there isn't one. Taking that a step further, atheism becomes a religion. A moral philosophy shared by a community that seeks to explain (or at least understand) mankind and it's place in the universe. That they are gathering in the same place, at the same time as the religion they reject is rather curious. They seem to be trying to co-opt the church rather than avoid it.
If someone revealed this all to be an elaborate hoax or prank I wouldn't be surprised.