With my FF core 18.104.22.168, impossible to have a good filter black&white and color with conditions or printer filter.
Please look at the file bmp joinned.
That check is in the job ticketing section. As such it would rely ont he print ticket (JDF or XPIF) specifying the desired color mode.
However, you should be able to route based on the contents of the file via preflight.
Build a preflight profile in acrobat to flag jobs that will create CM or Y content when separated:
After you do that route based on the preflight result (e.g. warnings go to the color printer and everything else to the mono).
That should do the trick.