It depends on whether you play that the "followers" (the term I'll henceforth use to describe wargear models that accompany a character) join/become part of the unit their character joins or are part of.
In some cases (like the Ork codex) the rules are clear that the followers join the unit while the character is part of it. Other followers (like a SM familiar, for example) do not specify.
I think most people play that followers join the unit when their character does (i.e. followers can/must be removed as casualties when that unit & its joined character suffers damage from shooting, for example).
Under this presumption (that the followers join a unit their character joins) then while the IC would still fight combat seperately, his followers would fight as part of the unit the character was joined to.
However, if you play that followers do not join the unit their characters join (i.e. their rules don't specify) then you would play that the enemy is fighting 3 distinct elements in CC, the character, his followers and the unit the character is joined to.
Of course, when playing with the latter interpretation, much more difficult rules situations will start to arise as the character is joined to a unit but his followers aren't. How do the followers take damage from shooting? What about morale checks, etc?