I just offered the Iridium a Free Trade Agreement. One turn after I could not see any increase in my income, so I looked in Diplomacy under Treaty Details: Nothing to be seen of any benefit for me, it says "Weekly revenue from treaties: 0.0 bc".
Is that still the old bug that treaties only benefit the party that it is given to?
Btw, in the Treaty Details there are also a lot of "New Game" entries. I think that's for all the positions where I traded resources, seems the game picks a wrong string there.