This cover has always reminded me of the discrete abstract shapes and contained blobs of color in Miró's "Constellation" paintings—this resemblance may very well have been intentional, especially since Breton himself, a few years before the American publication of Nadja, had composed a series of "Constellations," prose poems in response to the symbolic language of his fellow Surrealist.
I haven't read Nadja, so this attempt at tying it back to Police, Adjective is bound to be a bit dicey. But Breton's "Surrealist love story" is actually comprised in large part of the reflections of the first-person narrator, blending observation and memory during his walks through Paris.
One notes that the protagonist of Police, Adjective, locked into his daily routine of largely uneventful surveillance, has ample time for reflection (one might also suggest that the Kafkan bureaucracy and obsolete legal code depicted in the film seem more appropriate to the 1920s than the 2000s).
The book begins:
Who am I? If this once I were to rely on a proverb, then perhaps everything would amount to knowing whom I "haunt." I must admit that this word is misleading, tending to establish between certain beings and myself relations that are stranger, more inescapable, more disturbing than I intended. Such a word means much more than it says, makes me, still alive, play a ghostly part, evidently referring to what I must have ceased to be in order to be who I am. Hardly distorted in this sense, the word suggests that what I regard as the objective, more or less deliberate manifestations of my existence are merely the premises, within the limits of this existence, of an activity whose true extent is unknown to me.
And so on. It's astonishing, reading this, how applicable this narration seems to the character of Cristi in Police, Adjective: a young man whose own conscience is subsumed in his job of "haunting" (secretly surveilling) the subjects of his investigation, largely against his will.
In the film's great climactic scene, Cristi's boss pulls out a dictionary and demands that Cristi define words like "conscience" and "police," demonstrating that Cristi's own sense of his self and his codes of behavior are, in fact, objective only as far as they don't contradict with the objectivity of dictionary definitions and Romanian law, whose true extent and purposes remains opaque to him.
(In his discussion of the film, the L's Henry Stewart noted that "the cop has a habit of emerging from the margins of frames, almost spectrally—like a held-over ghost, perhaps, from a secret police past.")
So. Is this incidental bit of background itself a symbol, referring to Police, Adjective's secret identity as a remake of Breton's Nadja? Almost certainly it is not! But I do understand paranoia a little better, now that I've gone looking for esoteric connections and actually found them.