There are no references to ensouling, though there are references to ensouled creatures, is that what you mean? It means quite literally any creature creature that possesses a soul. In almost all cases, this generally means any living creature, most undead, and basically never constructs (unless you've got a Warforged type situation going on like Wyrwoods).
Do you mean whether a Conjuration companion itself can use an implement (if it has casting ability itself), or if they benefit in some way from their caster using a Conjuration sphere implement when summoning the companion?