I don't have much ready to hand - and it may be hard to come up with hard proof.
There is Greenwald[0] and the infamous Homeland Security Disinformation Best Practices and Safeguards Subcommittee - here are the bios[1]. Note how interlinked these people are. They don't need to document their interactions, because they basically think alike and know what to do without specific instructions. The FBI acts as the primary point of contact from the letter agencies, as per the title if the article we are discussing. The Beltway revolving door takes care of the rest of the interactions, including providing experts to the media, so the rest of the Beltway can just listen and act.
[0] https://greenwald.substack.com/p/congress-escalates-pressure...
[1] https://www.dhs.gov/sites/default/files/2022-07/HSAC%20Disin... [pdf]
If the Congress wants to force companies work with the FBI, they have the absolute power to do so.