Ah, okay. I was imagining you were talking about stop spacing of 2-3km. Spacing similar to B/D sounds pretty good.
What I imagine isn't as elaborate as, say, the
1968 plan
/s for tunneled streetcars (which is like a predecessor to the 1985 DRL). But rather something simpler than the 1946 plan WKlis posted, and similar to the return of that plan with its vicennial
1966 counterpart. In the 1966 plan, the essential component was a short underpass to bring the line below grade through the central area. East and west of, say, Sherbourne and Spadina, surface operation and upgrades would work very well. In the central area however below-grade was seen as critical to the line's success/reliability.
Surface enhancements that come with an active transit street are well known and I agree have tons of merit. They work very well in places like Calgary, or historic downtowns in many European cities. But I consider Toronto's core/CBD a different animal entirely. Tiny blocks, hundreds of thousands of pedestrians, +80s towers (and never-ending proposals for more), inevitable 'slow orders' during peak times and events... these would definitely cut into service/reliability. There really is nowhere else in the country like our downtown, and I don't think there ever will be. I'd definitely agree with closing much of the street to cars, but I think the streetcar needs to be below grade in this area.
I think comparing what Gweed proposes to many European cities is very apt. However it's also common in Europe to see stadtbahns or premetros or whathaveyou, where trams dive under the central part of many cities. Similar to SF, or Boston, or what we have on Eglinton: i.e - surface in the outer area, tunneled in the central area. But while Eglinton was bestowed with a whopping TEN KILOMETRES of tunnel, this would be more like 2.5-3km.