You'll find several discussions about this in the threads for buildings in this area, including this one, but I suppose that i has been a while since we've gone at it. Quickie version:
- The City wanted a gradually skyline in the area hat gradually decreased in height from the Financial Core over to Spadina Avenue (and then a big drop west of Spadina). It's been referred to as the 'clothesline', as if one were tied to the top of First Canadian Place and then run across to The Hudson: no buildings were to pop through that descending line.
- The developers of Festival Tower applied for a exception to that, and were granted it based on the benefit to the city that the Lightbox would bring: they needed the density (and height) to defray the costs of building the TIFF infrastructure below. After negotiations with the City, they got approval.
- Developers of other nearby buildings applied for exceptions and the City said 'no'. The those projects were appealed to the OMB, it said yes, not caring whether the other buildings were bringing a benefit to the city or not, the idea being that if one project was granted a certain height, that was precedent enough for granting that height everywhere in the neighbourhood.
Thus, 157 metres rules.
42