I can quickly add to the discussion.
To your point, interdisciplinary research is often the intersection of where very interesting science happens, so beyond the chairs and the tri-agency programming, we do of course collaborate across the agencies across several specific calls.
We also encourage where there are at least two different disciplinary areas; we have a specific program for that. If somebody is doing something that meets at the intersection of SSHRC and CIHR, we're able to accommodate that on a smaller scale.
At NSERC, we have over 21 collaborations with other science-based departments and agencies, so we really wanted to connect that science that is happening in academia with the federal government.