Leary was previously general manager of York Region Transit and held senior roles with the Massachusetts Bay Transportation Authority (MBTA).
[7] In 2014, Leary was hired as the chief service officer of the Toronto Transit Commission (TTC) by then-CEO Andy Byford.
[11] In December 2017, Leary was made the interim CEO of the TTC, when his predecessor, Andy Byford left to head the New York City Transit Authority.
[13][14] In late 2023, TTC Chair Jamaal Myers attempted to have Leary suspended while an investigation into allegations of workplace misconduct took place.
[15] Leary noted that it was his decision to leave, having waited to announce his resignation until contract negotiations with Amalgamated Transit Union Local 113 had been agreed.