Toronto's construction speed isn't that bad, especially office towers and condos. Public projects are much slower but it isn't outrageous compared to other western cities. What is really slow is the time spent in design/EA etc. It seems to take forever to just get the shovels in the ground. That being said, the government should realize by speeding up construction speed by careful planning and simplified design etc, you can actually save a lot of money...
Talking about China, it isn't all that fast. It really depends on the scale of the project and the location. Some places have more funding from the central government thus faster. Here are some examples I know, they vary greatly:
* Beijing subway line 4 (28km, mostly underground): 2003-2009, 6 years.
* Tianjin metro line 9 phase 1 (46km all elevated): 2001-2004, 3 years.
* Tianjin metro line 9 phase 2 (7km underground): 2008-2012, 4 years.
* Hangzhou metro line 1 (50km mostly underground): 2007-2013, 6 years.
* Tianjin metro line 3 (30km, mostly underground): 2008-2012, 4 years. [Almost 2 TBMs per every 2 to 3 stations]
* Tianjin Railway Station renovation (also adding a giant underground complex containing 3 subway lines): 2006-2012, 6 years (station closed for 2 years).
Speaking about Union station renovation, the last one (Tianjin Railway Station renovation) I think is somewhat comparable. The project included:
* two new road tunnels under the station
* an underground parking garage
* a bus terminal and underground bus platforms
* rebuilding of the elevated waiting area
* rebuilding of all platforms and rain sheds for HSR
* renovating of the old station building
* a large underground multi-modal transfer complex providing transfer to 3 subway lines.
Demolition of the old structures and platforms started in late 2006. The station was completely closed and a temporary station was constructed at a different location. The temporary station was extremely basic but it did the job. The new station reopened in summer 2008 in time for Beijing Olympics and the temporary station was then demolished. At the time of 2008 opening, all projects were done except for the underground transfer complex. It was one of the largest underground structure in China at the time. It took another 4 years to finish and opened with 3 subway lines in 2012.
Two points here:
1. Union revitalization would be much faster if it's closed completely for a year or two.
2. Underground structure is slow everywhere. So if Union was to have a new elevated waiting area above the tracks instead of digging deeper into the existing waiting room, it would probably be much faster as well. The new glass train shed is almost as big as a waiting area...