Personally, I've found 511 a times, quite slow both north and south at the bottom of Bathurst, particularly south of Front.
If you look at the city mapping, the width of Bathurst is the usual 20 metres (66 feet or one chain) north of Queen. BUT from Queen to Lake Shore it's 30 metres (99 feet - or 1.5 chains).
You can clearly see this change in width if you stand on Bathurst just south of Queen. This is also the reason there is space for all those islands on Bathurst south of Queen for streetcars (and why there is one at Queen northbound but not southbound).
There's no reason they can't run a streetcar ROW all the way from Queen to Lake Shore. And in my experience, once you are north of Queen, the road flows better anyway.