The fleet will be formed into two or three-car sets seating up to 180 passengers and comply with US Environmental Protection Agency (EPA) Tier 4 emissions standards.
The vehicles have been designed to enable straightforward conversion to electric traction if required, and an environmental assessment on electrifying the route is currently being carried out.
The trains are due to be introduced when the airport rail link opens next year, operating a 15-minute interval service between Union station in Toronto city centre and Pearson Airport throughout the day.
From Union station, UP Express services will run along the Kitchener Line for 22km, calling at Go Transit's Bloor and Weston stations before diverging onto a new 3km elevated branch, which will follow the route of Highway 409 to reach the airport station at Terminal 1.
The $C 456m ($US 418m) 30-year build and maintain concession for UP Express has been tendered as an Alternative Finance and Procurement (AFP) project.