I understand exactly what you're trying to say, and the point i'm making is that you cant base your point off of Google Maps. Even if you look at the map, you would understand that this plan would require expropriation.
Every single piece of property between between Martin Grove and Islington would be affected, including 2 TDSB high schools (Martin Grove to a lesser extent, and Richview to a larger extent). If you look at the section between Royal York and Scarlett, it would still require expropriation as it would affect most of those properties. The only section where expropriation wouldn't be needed is the section between Islington and Royal York.
There's no overthinking and over-complications going on, it is simply fact and there's more to building trenches than just digging a hole in the ground. Soil conditions, and engineering play a large role so any trench in this area could be bigger than you would think.