While I don't think that Toronto has too low of a limit everywhere, especially in the city, it does have an issue of posting low limits on many roads, especially larger roads specifically designed for higher vehicle speeds.Surely you mean the polar opposite of this.
Roads like Don Mills or the Bayview extension for example. The Bayview extension has 0 sidewalks, and the adjacent bike lane is barrier protected, yet the city tried to stick a 50 limit on it (luckily reversed). In any other municipality in the province that road would have a 70 or even 80 limit as it's designed for those speeds and doesn't have any pedestrian traffic to protect.
Don Mills is a 50 limit as well, despite having very low pedestrian counts, sidewalks well separated from the street, and being designed for much much higher speeds. It shouldn't have been dropped from a 60 limit. The standard of road would likely have resulted in a 70 limit in other municipalities. A 50 limit makes sense around Eglinton and Lawrence as pedestrian counts are higher, but north of that the ped counts are low and the road built to very high standards.