Although I would place the primary blame for the incident with the Tower for not verifying that the Piaggio was clear before issuing a take-off clearance to the cirrus. This being said however, what was the Piaggio crew still doing short of the intersection over the 40 seconds after their clearence was issued? I think that getting approved for a short delay may have been in order. Also, if the cirrus had looked left and right before simply jamming the power forward, the incident would not have occured like this because those departure points are easily visible to one another.