Back in the mid-1990s, Ontario Hydro surplussed one of their transmission corridors in Scarborough. The segment was located between Warden and Pharmacy, and ran from the Finch Hydro Corridor (the one north of, and parallel to, Finch Ave) to the Gatineau Hydro Corridor (the one runs diagonal north of Eglinton Ave). The portion of the corridor located north of Highway 401 was sold to a residential developer, and resulted in a very interesting residential infill project.
When the lands were surplussed, the former City of Scarborough adopted an Official Plan amendment to designate the corridor lands as Open Space. Ontario Hydro and the developer appealed this decision to the OMB. The developer had proposed 666 residential units (around half single detached and half semi-detached), some parks and open space, and a little bit of neighbourhood commercial. Due to the narrow nature of the corridor, in order to accommodate the development, the lots and all building setbacks had to be smaller, and the roads narrower. If you look at an aerial photograph of the area now, it is immediately evident that the corridor development is notably denser than the existing areas that surround it. In 1998, the OMB allowed the appeals and, thus, the infill development.
The OMB decision hinged on the City's inability to quantify how the infill development would lead to "undue adverse impact." Put another way, if there wasn't an impact, there wasn't a reason it should be prohibited. Though I could not find the complete record of the OMB case online, it appears that the City might have attempted to appeal the decision to Divisional Court. The fact that the development exists today suggests that if they did, it clearly wasn't successful.