"Some animal-rights advocates worried that the bill could lead cat owners to abandon their pets rather than risk a fine or pay for the procedures."

That line right there is my biggest fear. I don't think any shelter in this country should allow animals out the door with out first having them spayed/neutered, and I'd love to see the day that landlords make it manditory to have your pets fixed (if they allow them). Many of the cats I pick up are from slumlord areas where as long as they get the rent, they don't care if Fluffy & Studly aren't fixed and on the streets. It's a great idea if it works, but there's plenty of persons that refuse to fix their pets even if it's for free.