The 5-km extension that they re announced on page 1 of this thread, a decade ago? Well, it looks with the federal funding announcement, that it might indeed open before the 2020s are out.
Yes, if you count the every 15-minute off-peak RER-rail like service on the three northern REM spurs, that is not in a subway (except under the airport runways at Dorval) as subway, but neglect the 30-km of Line 5 and Line 6, 23-km Pearson RER-like service in Toronto and the 106-km Oshawa to Aldershot (and hopefully 70 more kilometres on 3 other lines, from Union to Bramalea, Unionville, and Aurora) RER-like service which should be running in the 2020s (part of it is 15-minutes mid-day already), then Montreal will have a bigger subway
The REM is an odd hybrid - a red-headed stepchild. The 8-km piece with 7 stations from Bois-Franc (hopefully an Orange Line transfer station one day) to Edouard-Montpetit (Blue Line) with every 2.5 to 5 minute service is very metro-like ... and part of the original 1961 Metro proposal. As is the next 4-km from Edouard-Montpetit to Central (Bonaventure). This 12-km line is nothing short of brilliant, and long over-due. Then the 16-km southern piece of the line from there to Autoroute 30 on the South Shore, will also have very 2.5 to 5 minute service - though only has 5 stations.
So that's 28-km of very metro-like service on the REM
But the remaining 39 km of the REM only adds 12 more stations, and the service is more more like RER (15-minute of-peak). West of Bois-Franc it branches into 3 much more suburban services, with the next station ranging from about 6.5 km (Sunnbrooke) to 9 km (Sources) depending on the branch.
In reality, both cities have had transit stagnating for years. It's been over 30 years since the last Metro station opened in Montreal, with only 5 km and 3 stations built in suburban Laval, north of Montreal in the early 2000s. Toronto has fared only slightly better since then with 16.5 km and 11 new stations in the last 30 years.
And now both cities are seeing the greatest transit expansion in over 30 years. For all the comments about which one is better, and measuring who has the biggest extension, the similarities far outweigh the differences. Can we just discuss the project without the needless comparison.
Perhaps the thread itself - which refers to the long-cancelled 2009 announcement of over 25 km of extensions to the Blue, Orange, and Yellow lines, by a long-banned user, should be renamed.
Regardless of whether or not REM is what we traditionally locally call a subway, there's no question that it's a metro by any definition.
For the 28 km east of Bois Franc - absolutely. Personally, I wouldn't call every 15-minute mid-day or weekend service as "Metro". If it was only very late at night ... sure. But not at mid-day. I think that frequent service is required - and in a Toronto context, that's normally a minimum of every 10 minutes. With every 6 minutes being the off-peak minimum on Line 1 to Line 4 (though it's slipped a bit to 6.75 minutes on Line 3, off-peak, with the rehabilitation-related service cuts).