I was watching the 1988 Grey Cup game on TV the other night. It was in Ottawa, and it looked pretty sold out to me.
The 2004 Grey Cup was a huge success - sold out.
Now I'm watching the Mitchell Bowl on the lousy Score (note, the Score is good for something, that being broadcasting CIS games, but they still are head-over-heels in love with the NFL and tend to pay minimal attention to the CFL). The game is in Ottawa, and it looks like there's a really good crowd there, for university ball. The stands between the 35's are completely packed with people.
As for the Renegades, they had 20,000 people out to games when they had the worst owners in the League. Not too long ago, Hamilton, Toronto and BC all had worse attendances.
Ottawa fans have had to deal with crap ownership (and that's being REALLY nice) for the past 20-30 years, and they still come to the games. If Ottawa gets a good, strong, committed owner, they'll be fine.