I looked at the Tucson City Code. Honestly, you're lucky that your city has their code online. Most don't yet.
Anyway, if you go here, http://livepublish.municode.com/2/lp....htm&vid=11294
and choose Chapter 4, Animals and Fowl, then Article 1, In General, that is the code that pertains to cats. One part, Sec. 4-6 states:
|It shall be unlawful for any person to harbor or keep within the city any lost or strayed animal. Whenever any animal shall be found which appears to be lost or strayed, it shall be the duty of the finder to notify the animal shelter or pound at once.
But, ferals aren't strayed or lost animals. They aren't "owned" in a traditional sense.
However, for one of your questions, under Sec. 4-9:
|(c)Owner means any person owning, keeping, possessing, harboring, maintaining or having custody or otherwise having control of an animal.
So, maintaining the animals legally makes you their owner.
In reading all of this, one thing I do not see is any kind of pre-ordained "limit" to the number of animals you may keep. There are clear cut guidelines to neglect and cruelty, but not a limit.
And really, all of it leaves your entire question open to interpretation. As Mark has said numerous times in the SOS threads, Animal Control doesn't usually go looking for animals to impound. But if there is a valid complaint, then they respond.
My suggestion is to call (anonymously!) the Animal Control and find out if they have any policies toward feral cat colonies and their caretakers. And of course, if you are outside of the true city limits of Tucson, none of this applies.
If that's the case, call your City's Clerk and ask if you can get a copy of the Code pertaining to domestic animals.