2014 Absa Cape Epic Stage 5 with Specialized Racing - YouTubeI haven't done it but I heard its a bit of a 'roadie' mtb stage race, very fast pace with not a huge amount of technical stuff. I would imagine you would need to do a very high percentage of training on a road bike. Others will be able to help more though I'm sure.
And look at the rest of the riding they show in the video.2014 Absa Cape Epic Stage 5 with Specialized Racing - YouTube
From today's stage 5.
Note the comments at 1:28 RE: 'roadie' mtb race.