Ultimately, any enforceable agreement (whether it's a contract, a MOU, or something else) is defined by the terms and conditions contained therein. After contacting the question originator, it was explained that the Government to Government relationship was some sort of work agreement. There is nothing in the regulations, or elsewhere, that I'm aware of that say you absolutely can not use CDRLs in such a situation, but that doesn't mean it makes the most sense to use them any/everywhere. The DD1423 form is very well defined in terms of the information it contains and conveys between the parties, but it would seem it might be beyond the scope of what might be needed for some sort of working agreement between 2 US Government agencies. You might also want to consult the following links to explore the topic:

1) DAU's new CDRL Planning Tool - Contract Data Requirements List Planning Tool (CDRL Tool) (dau.edu)

2) DAU News - Product Support Contract Data Requirements List (CDRL)