I noticed one of my ground officers was assigned to a unit I did not produce. It appears to actually be a ground unit owned by one of my civilian mining companies. Presumably the unit is stationed on the mining comet as some base security. However, I cannot see or have any access of this unit (as far as I can tell) outside of this indirect confirmation through my officers.
It would be nice if civilian ground units were listed in the formation menu, as civilian ships are.