Red Eclipse is a total conversion of the good old Cube Engine 2. This made it quite easy to generate the same munin graphs, which i did for OpenArena, Sauerbraten and Teeworlds in the past, for Red Eclipse too. As a result you can track the utilization of the server on this page.
Just for the record: At the moment the OpenArena and Sauerbraten server are frequently used. Teeworlds gets less attention because of the huge choice of different servers. I think, all in all, things are looking good at the moment.