Keep in mind the new bridge is being built where the existing bridge was. So after the one night demolition over 401, there is still a lot of removal work to be done at each pier, abutment, etc.
Then the new foundations and piers, etc. have to be built for the pedestrian bridge, and the workzones on Highway 401 below must be configured to allow access at those locations. So it will probably be a full year or more between the closure and opening of the new bridge.
Once the bridge is down, they have to excavate the embankment to allow for the new collectors lanes and building the embankment pier.
I stand to be corrected, as its been too long since I was at a meeting and seeing the plan, but I believe the new bridge will be steel.
If its steel, you can build the foundation to support steel piers on either side of the current 401 and in the centre. Doing the centre will require traffic being to the right to allow the building of the centre pier.
Once all the foundation is in place and the embankment piers, the 401 will be close one night to allow the erection of the bridge piers and the bridge over the current 401 lanes. The bridge over the new collector lanes will happen at the same time, but don't require the 401 to be close to do it.
If steel, it should be box frame 100% completed as 4 sections to be lifted into place.
Once that is done, then both ends will be rebuilt to connect to the bridge.
If all the piers are concrete, will take a longer time to build them steel.
The earliest you can see the bridge open is spring 2017