In Indiana a Basic can use a combitube and do IV maintenance. Limited in drugs (O2, nitro, ASA, glucose, epi, activated charcoal, and some meds with medical direction) and can't do manual defib of course.
Intermediates are recognized but it seems a waste of time to go through that training without getting your cert as a medic.
I highly doubt you'd be able to have any type of reciprocity with any state and would expect you to have to go through an EMT class. At the very least you'd obviously have to take the written and practical and pass National Registry.
I know quite a few firefighter/EMTs but most worked for private companies before getting on with a department. Any municipality will be difficult for you to get on without some type of foot in the door leverage.
I'd follow your original plan of finding a private company to work for. Don't work in IL. They are so limited by what they can do as medics that it's pathetic.
The southwest and midwest states are good areas to look into. Contact a state's EMS office for more information.