Actually, I believe Willian may have been referring to what I describe in this post for exporting a LUT including IDT, RRT and ODT directly from Resolve. But that is reliant on replacing Resolve’s built in IDT with one written in DCTL (such as the ARRI, RED and Sony ones I sell). But since, as you point out in your original post, the BMD Film IDT is not published, it is not possible to rewrite it in DCTL.
I did try deriving a matrix for BMD Film by running test patterns through the Colour Space operator in Resolve. But my result did not match it exactly. I can only assume that BMD apply some “secret sauce” to processing of images from their own cameras, which is not easy for third parties to replicate.