Shakey can't ride because is contracted with KTM and KTM won't let him, or Kenny won't pay for KTM to let him, most likely. I woudn't be surprised if McWilliams does for "expenses paid" only.
Having just looked at the riders list I began to wonder which ones are in danger of loosing their MotoGP spot next year. I reckon that Bayliss, Xaus, Roberts, and with the exception of Nakano at least one of the Japanese riders won't be on the grid next year.