But here's an interesting quote:
However, a March 2009 ruling by the Supreme Court of Canada on political ads on buses found that limits on advertising violated the right to free speech.
"This is something the community is going to have to get used to because there isn't a lot we can do about it," Jeff Bohach, a City of Regina spokesman, told CBC News.
UPDATE at 11:47 PM
Lifesite has a couple of pictures of the ads.