SimGuruGraham has confirmed that the three mentioned above will NOT spawn in “downtown” worlds like Bridgeport! Sweetness!
I know some understand why they did this, but other do not. Think of Bridgeport as a major city similar to Downtown Los Angeles, New York Times Square or Downtown Tokyo. In these places, you will NEVER see wild deer or horses. Maybe a raccoon, but that would be at night. This is why EA has done this. Wild horses running down main street in NYC doesn’t happen, thus it’s the same way with Bridgeport. Also, to know which towns will and will NOT allow wildlife in Pets, look at the pic below.
If a custom world has the same buildings icon that Bridgeport has (on the left), wild life will NOT spawn in that world. However, if it has the house icon that Sunset Valley has (on the right), they WILL spawn in that world. I hope this clears up any confusion that anyone might have had about this.