At first, they were adversaries — the taxi agency leery of a smartphone app that could upend decades of street-hailing history and the business that responded by hitting the tech-friendly Bloomberg administration where it hurt.

The company, Uber, would subsist in “more innovation-friendly cities” like Boston and Toronto, its chief executive said in 2012. Its six-week, legally questionable stint inside New York City’s yellow cabs, which had allowed drivers and passengers to find each other with the touch of a phone, was over.

But more than 18 months later, with the technology now approved by city officials and accepted by riders, it seems the relationship has been consummated in earnest.

A top official at the Taxi and Limousine Commission, Ashwini Chhabra, is leaving for Uber, he said on Monday, becoming the company’s first head of policy development and community engagement.