It is as close to poetry as narrative fiction may be while remaining prose. The 'poetry' of Iris Murdoch is in the fictive use of symbols, and in the philosophic mood of her fictive intentions. These points would seem to advise against turning her attention toward formal verse in the lyric mode, having marshalled her resources elsewhere. Her experiments with fiction are experiments of language, but also of narrative. Her use of symbols works by what is left unsaid of their impulse.
Lyric poetry is a personal voice.
In modern practice it tends to the confessional. We assume that the 'I' of a poem is the 'I' of the author. We feel cheated by the use of the first person as a narrative guise. That is for fiction. Discerning private intentions in an author is a speculative trespass.