Ryan,
I would recommend being completely honest with anyone that you apply with. Even saying that it was a long commute could be conceived as a lie by people, which, in my opinion it really is.
My suggestion to you is that is non specific, yet coaxes them to inquire further. That way you are able to explain what really happened in your own words.
I gurantee that any prospective employer will find out what happened at the ambulance company, whether it is as rumor being circulated by the co-workers that you worked with, or as "off-the-record" truth from your supervisors.
Even though supervisors are not legally allowed to black list or slander an employee, it can still happen. If they do it, it makes tham look bad. Especially if the issue is already out in the open. If you lie about it, however, it exposes the lie, you get rejected as a candidate, and you also get a very poor reputation as a liar.
As I am sure you already know, the fire department is a profession that is widely connected. Believe me, rumor and truth spread like wildfire. Your possible reputation may very well preceed you at the next department that you apply for.
Be smart when you apply for departments. Not every bad thing can hurt you . You need to remember that every one has done at least one stupid thing in their life. You're not the first one to screw up. You want to be that person that grows from his mistakes, not one that continues to make more on top of them.
Every thing in life, both positive and negitive, can become an asset if you know how to apply the lesson in the outcome. Be brave, take large strides forwards. Lies become cowards, who constantly back peddle.