Kelly, I'd recommend calling the City of Missoula and requesting their statistics since allowing Urban Chickens, or Bozeman, or Livingston, or Laremy, WY, or Kalispell--I have. There is ample info online regarding Urban Chickens in any number of major cities including Portland(OR and Maine), Seattle(WA), Riverside(CA) and lets not forget New York City where the Dept. of Health has declared that Urban Chickens are not a threat and people can keep as many hens as they'd like.
The ordinance saying it is lawful to keep up to 6 hens (no roosters)in MC has already passed the City Council and went into effect June 24, 2011. Now we are hammering out the specifics. I have repeatedly encouraged adopting the Missoula Ordinance--it addresses any potential concerns but doesn't make it so restrictive citizens will have a hard time complying. Plus, they have a 5 year track record IN Montana. And since you mentioned concrete (included in the minutes not yet approved), I would assume you were at the same Public Safety mtg I attended and heard Councilmen repeatedly say, "I don't know anything about chickens."