Tenmei and MAgno

Exactly why is Tenmei on MAgno's crew? I mean, seriously. Tenmei is a spy for Tarak against Majere. Why on earth is he on a pirate ship who is not part of the MAjere government to begin with?
Is it because MAgno Vivan is somehow related to the MAjere government and Tenmei signed on with them to see how? Or is it some other reason? What would make MAgno's crew more important to the Tarak intelligence Bureau then a position in the goverment would?