I'd probably say not a good idea. The forces that are put on a saddle in cross are much different than raod and mountain biking. I've seen saddles of different types break when put through the rigors of cross dismounts. I'm not sure that the carbon saddle would be any worse in terms of longevity, but it's an expensive part to have to replace. Especially when there are more economical options that will likely provide the same service.
Is there a reason you were looking at this saddle in particular?