They will apparently be playing Random Draft mode, which normally means that it works similarly to All Pick, except for the fact that the players pick from a pool of 50 random heroes. How this will work with the 18-hero pool is something I don't know.
It's not that clear. They call it "Random Draft", but this picking mode in Dota 2 doesn't mean "doing random picks". "Doing random picks" is the "All Random" mode.