Don't know when there will be an official CORE MP release, but each CORE release can be used for MP, just copy all the "core-mod" directory into the standard HOI directory and over-write all. Then you have to launch the game by the standard HOI .exe instead CORE batch file.
DISCLAIMER: This should work without problem, but I personally never tried it.
DISCLAIMER: This should work without problem, but I personally never tried it.