Don't know if you're still around that grey hell of a city, but I'll try to give you and the other vagabonds some ideas:
- Depending on what you and your pack look like (can you pass for a normie?), you can often get into hotel stairwells and sleep at the top, by the roof-access. I slept in the Westin's stairwell.
- Check the low buildings downtown, especially in Sandy Hill area and Bank St. I slept on a couple fire escapes there.
- Carleton University (and area) have parks and greenspaces that are fairly private -- but it's a bus ride or a long walk from downtown.
- Strip malls (on the periphery of downtown and the city) have ladders on the back-alley-side, as everywhere. They are covered with steel doors, but you can work your way up most of them and sleep on the rooftops without anyone bothering you.
Hope that helps.