The Fairfield Plan is in draft form, here is the latest version (.pdf)
Consider development of 3 to 4 storeys, with some added floor space, where the
provision of non-market housing is considered. In support of this goal, buildings
of up to 5 storeys may be considered along Fairfield road,
So I guess it comes down to whether you believe 1720 Fairfield is close enough to be considered part of the Fairfield Plaza urban centre.
I just can't see a judge looking at these documents and saying a three storey building is explicitly forbidden.
The spirit of both the OCP and Plan hinge on preserving SFD neighbourhoods by densifying urban hubs. A border case like this has a lot of room for interpretation and I don't understand how a court can resolve it.
"[Randall's] aesthetic poll was more accurate than his political acumen"
-Tom Hawthorne, Toronto Globe and Mail