The first train set entered service on 27 December 2020 and will become the primary rolling stock used in the Metro Tunnel when it opens in 2025.

[8][9] However, the Siemens units suffered major braking issues over the following decade, causing their repeated withdrawal from service;[10] when the State Government tendered for 18 further six-carriage trains in 2007, it restricted bids to the previous two models ordered and awarded the contract to Alstom.

[13] The NDPMR's first stage, intended to be completed before 2016, acknowledged the need for an interim solution of several more X'Trapolis trains to overcome major constraints,[14] as well as recommending the internal reconfiguration of Siemens and Comeng trains to increase capacity,[15] but identified the provision of new rolling stock as critical to the cost-effective use of existing railway infrastructure.

[17] The NDPMR envisaged that these high-capacity trains would completely replace the Comeng fleet by 2032, and be used primarily on the Sunshine–Dandenong line created by the Metro Tunnel.

The Coalition's proposal was criticised by the Labor opposition led by Daniel Andrews, labelling it a "con", and that 25 trains were "not enough to meet future passenger numbers".

[21] Labor's proposal would involve the purchase of 37 new trains via expressions of interest, and an expanded scope of the Pakenham and Cranbourne line upgrades.

[26][27] By September of the following year, a full-scale mock-up of two carriages had been constructed and was presented to Minister for Public Transport Jacinta Allan.

[28] The mock-up was made available to drivers, technicians, representatives of the Public Transport Users Association and passenger groups including the visually impaired and those with physical disabilities.

The Evolution Rail consortium noted that this last stage in the design process marked the fulfilment of the project's first major contractual obligation.

[29] In late 2017, the Locomotive Division of the Victorian Rail Tram and Bus Union lodged proceedings in the Federal Court of Australia against Metro Trains, claiming that the consortium, government and Metro planned to introduce a lower standard of training for operators of the HCMT.

[31] This followed criticism by the Australian Workers' Union of the decision to award the contract to Evolution Rail instead of Bombardier, the latter of which had an established manufacturing operation in Dandenong.

[34] By June of that year, manufacturing had commenced, with the first body shells arriving at Newport Workshops from CRRC's facility in China.

[35] On 9 May 2022 the Victorian Government announced it was procuring an additional 5 HCMT sets for use on the Melbourne Airport rail link, to bring the total order to 70.

[32] CRRC Changchun is leading the development and design for the HCMTs, and is manufacturing the train bodies as a joint venture with Downer Rail.

[53] Twenty-eight wheelchair spaces and wide aisles between seats enable easy access for passengers with disabilities.