what i've read about it, the police claim it's not entrapment. basically, the absurd excuse goes like this: he could have easily said, bitch i will let you smell my dick at home, let's go.
instead he just whipped it out, exposing himself in a public place.
however, the fact that she asked him to sounds like the entrapment part. if she had said something like, well i'd like to get a better look at you, AND THEN he whipped his dick out, well that sounds like his fault. however this sounds like she said, show me your cock, and he did.
police did something similar in NY subways. they left bags of stuff (money, an xbox, a cell phone) and then arrested people who picked it up and walked away with it.