The first phase, between Plaza Once and Caseros, which opened on 18 October 2007, currently stretches over 8.8 km between Hospitales and Facultad de Derecho stations.

According to projections, the line will stretch a total of about 11.85 km and will run from between Retiro to Sáenz once the remaining sections are constructed.

[5] As the line was extended and passenger numbers increased, the rolling stock was replaced by new Alsom 300 Series units ordered from that company in 2012 in order to make up the entirety of the Line's rolling stock.

[11] The Facultad de Derecho station (located at the University of Buenos Aires Faculty of Law) was originally intended to be located across the road next to Plaza Francia, however concerns that it would damage the prestigious Recoleta Cemetery necessitated revisions to these plans and therefore delayed construction of the station, which eventually opened in May 2018.

[12] The final stretch to Retiro is not set to open until some time after the revision of the route following the relocation of the Plaza Francia station.