Carnival Phantasm, huh? It features characters from Fate Stay Night/Hollow Ataraxia, Shingetsutan Tsukihime and other TYPEMOON productions. Actually I’m not sure if this will be made into an anime, but I was told it will.
Here’s a character introduction:
Seems like it’ll be quite fun to watch. I’m looking forward to the release date (2011.08.14)
ANN says it’ll be a single OVA.