They are currently the only ones in Toronto compatible with the communications-based train control (CBTC) system, which replaced the legacy fixed-block signalling system in several phases on Line 1 between 2017 and 2022 (starting with the Line 1 extension to Vaughan Metropolitan Centre station, which opened on December 17, 2017) and has used only one operator since November 2022,[6][7] who plays the dual role of driving the train and of opening and closing the doors.

[2][10][11] On May 6, 2010, the TTC voted to exercise a contract option with Bombardier for an additional 186 cars, making 31 six-car fixed train sets.

It was unveiled to the public and media at Downsview station (later renamed Sheppard West in mid-2017 in preparation for the opening of the extension to Vaughan) on October 14, 2010.

[23] The TR series trains are similar to that of the T-series cars, also built by Bombardier in the same facility, but have several new features that make them more accessible and user-friendly for passengers.

They include: Additional yellow plastic straps (placed underneath the HVAC units) along with audible door opening side announcements (based on direction of train travel), which is played after the "Arriving at" station announcement (except for terminal stations) to better assist visually impaired passengers, were installed in all TR trains as of January 2016.

[29][30] Councillors Karen Stintz (who later also served as TTC chair), Denzil Minnan-Wong, and Rob Ford (who became mayor in late 2010) were opposed to sole-sourcing the contract to Bombardier.

[31] In late September 2011, it was reported that some passengers with mobility devices were experiencing difficulties while boarding or alighting the then-new TR trains.

[32] To increase mobility, the train does not have centre poles, leaving standing riders with fewer places to hold.

[34] In December 2012, the TTC announced that it had demanded a high-level meeting with Bombardier regarding ongoing performance problems related to "teething issues" with the doors.