With the planning of the VCC underway, Mario began to champion extending the subway to Vaughan, not just to allow residents to get to their jobs in Toronto, but also to help bring jobs north into the Region of York. He raised this notion early in Council and started conversations with Toronto and provincial officials, as well with York University, because he knew that with over 55,000 students at the time, it could serve as an added reason to extend the line.
Planning for the extension began around 1998 and two years later, the Spadina-York Subway Extension Committee was formed in 2000. Given his strong advocacy for the extension, Mario was the Founding Chair of the Committee. Included on the Committee were the Mayor of Vaughan, York Region Chair, the President of York University and two City of Toronto Councillors. The Mayors of Brampton, Mississauga and Barrie were added later to help give a greater regional view to the planning – something that Mario saw as an essential.
When Mario was elected Member of Provincial Parliament for Thornhill Riding in 2003, his wife, then Councillor for the City of Vaughan, replaced him as Chair. He carried his efforts and work at Queen’s Park.
On March 24, 2006 the Province of Ontario deposited its 1/3rd of the estimated cost to build the subway, in a bank account earning interest so that the earnings on the deposit would help to cover the expected increase in cost. On November 27, 2009, the official groundbreaking ceremony was held for the Toronto-York Spadina Subway Extension. Tunneling began in June 2011 and on December 17, 2018, 20 years after Mario started work on his vision, the 8.6 km extension was finally opened.