I don't think there are anti-trust laws. this information would be more governed by NDAs on the contract. However in reality the TMC will see the discounts in the GDS, they are usually given a copy of the contract and the TMC reporting should reveal the performance versus target. In short I'm not sure that the airline could tell the TMC anything it didn't already have access to.
There is the subject of personal information related to traveler FF programs and these are typically not shared and governed by privacy laws.
Is there a specific piece of information that you are concerned about that I could answer in more detail?