You may be right about Ottawa's BRT capacity. It was designed to be upgradable to rail (clearances, structural load bearing), and the BRT reached 90% capacity in 1996 for the number of *buses* used (180/hr), not for the number of passengers transported (it's been a decade since I learned this stuff, haven't researched since)
https://onlinepubs.trb.org/onlinepubs/tcrp/tcrp90v1_cs/Ottawa.pdf (2003)
And you're absolutely right that Ottawa's LRT didn't need to have the problems it has!