What has happened is that Metrolinx has been.....well.....overly optimistic with their requests for service changes and track slots. To the point of internally circulating potential schedules, train cycling and platform allocations for them prior to having everything finalized. (They do then send out the finalized ones in advance of the announcements, of course.) And the freight railroads have walked them back from it, telling them that they can only reasonably accomplish a portion of what they would like to achieve. And to Metrolinx's credit, in some cases the schedule changes that they've gotten have looked really substantial on the timetables (15 minute service on Lakeshore East, for instance) but have had a very, very minimal effect on the freight railroads dispatching and track allocation requirements.
But they are very, very protective of this, and have a requirement to not have the changes leaked prior to their own announcements. Which is why they no longer send the various transit agencies in the GTA the advance copies of the finalized schedules - they found that they would sometimes leak them.
Dan