As far as I know if you have a race surrender to you you know all it does, including ship styles of partners and enemies it has met/made. If you make a partnership agreement with an AI player who also has another agreement with another human player you should be able to see his ship designs as well. Pick and choose your treaties well!
If anyone has information contrary to the above, please correct me
"The Empress took your name away," said Chance.
Owen smiled coldly. "It wasn't hers to take. I'm a Deathstalker until I die. And we never forget a slight or an enemy." -Owen Deathstalker.