I guess that you mean the "Modal Neutral File"?

Actually this is a binary file format used by MSC Adams that contains the data of a flexible body. It can contain information like the invariants of the inertia matrix, the mode shapes and frequencies of the modal base derived from fixed boundary eigenmodes and constaint modes (through orthonormalization, Craig-Bampton modal synthesis) and the position of the chosen interface nodes and maybe other nodes (for graphical representation).

This data is obtained from a linear FE analysis (eigenmode analysis, substructuring) and the major commercially available FE-solvers can write this file ready for import in Adams.

The 'reduced' modal representation of the deformable body contains much less degrees of freedom than the original nodal representation as tze higher frequency modes are usually truncated.

To 'transfer' a transient analysis, you might have to build an analog model to the FE-model in MBS-software and apply the same time dependent loads at the same interface nodes. If you get similar results will mostly depend on a proper choice of the modal basis.

Not an answer, but a related question. How to read the Modal Neutral File outside the MBS software? Are there open-source codes to read this kind of binary file? Just curious.

I am also looking for tools to read a .mnf file, I need to import inertial invariants on Matlab. Does anyone know how to do it?