Saucy'verse Xander, after he sacrifices himself to close the portal, finds himself younger and with binocular vision in the Dresden'verse, but he doesn't have long to think about it because only a few seconds after he appears he hears gunfire and sees some guys in suits fending off...something.  Which he recognizes as never nice, so there's no dilemma in his mind about which side to support (hey, it's a legitimate problem--sometimes there are asshole humans doing bad stuff to good/neutral demons, and those situations don't always that way at first glance), and he swings into action, literally, considering the sword cane.
One of the men is John Marcone, who realizes pretty quickly that Xander needs wizardly assistance, where I don't know what happens other than he can't be sent back/send himself back, and has to stay in the Dresden'verse.  Something about the Laws, since Xander has to learn them and they have a different magical government (so to speak) back home.
Not sure how Xander gets along with anybody else, but he and Marcone get along like a house on fire.  Maybe he's not ecstatic about the whole mob thing, but Xander understands Marcone's position as a leader setting the rules and trying to keep his people in check, and occasionally having to do distasteful things because of it, so they hang out when Marcone's not busy, and Xander doesn't comment (morally, anyway) on Marcone's business.  If he ever meets Bob, he's reminded strongly of Anya.
Eventually he starts to come to the attention of people outside of the usual allies, because he's got skills and uses them when the situation warrants it, and he does hang around with some walking targets.