There are 28 separate agencies that accept EZ Pass (including the Illinois Tollway's I-Pass, Indiana Tollway's I-Zoom, and whatever Ohio's is gonna be called). They each have different setups as far as deposits for the transponders, periodic fees and replenishment requirements. Some charge an initial fee for the transponder, most don't, but like in Illinois, there is no fee for the transponder if you get it from the state or from a Road Ranger store, but if you buy it at Jewel-Osco there is a $2.90 fee that is imposed by Jewel-Osco.
Most have a refundable deposit for each tag (transponder), usually about $10. The PA Turnpike Commission's is $25. Sometimes the deposit is waived depending on how you set up your replenishment.
Inkasnana asked:
"Do they charge your cc each time you go through or is it a monthly bill?"
That's the replenishment thing. Some large fleets can set it up a little differently, but basically you build a "bank" with the agency where you get the tag. Instead of charging your credit card each time you go through a toll, the simply deduct it from your tag's account balance "bank". For example, you can set up the initial account balance to be $25 ($40 for Illinois), which is charged to your credit card. Each time you go through a toll, the account balance is reduced by that amount. When the account balance falls to below $10, your credit card is then charged a pre-set amount, like another $25 or $40, to replenish your account.
You can replenish your account by cash or check, or set it up for automatic replenishment via credit or debit card, or by direct EFT from your checking account. In most cases, automatic replenishment gets you benefits like waived transponder deposits or monthly fees.
You can manage your account online to do things like
- Update your license plate information
- Add funds to your account
- Update credit card information
- Review account activity
- Download account transactions
Which means you can print out a list of charges for reimbursement.
Cheri and Inky: With EZ Pass, only the registered owner of the vehicle can get one with some EZ Pass agencies (like in New Jersey, where you must own or lease the vehicle). That's not the case with the Illinois I-Pass (and I think the PA EZ Pass). You can get one for use in a rental car if you want. You can move it from vehicle to vehicle, just as long as you go online and add the vehicle and license plate to the account.
Wikipedia has a good rundown of the various fees and stuff that each agency charges. FWIW, when I got mine I looked closely at the EZ Pass from PA and NY, glanced at the others, went with the Illinois I-Pass.
From what you've explained though, I don't see how it would work out with our owner if we were to get I-Pass on our own, with no receipts to send to him for his taxes. I guess I need to do as Cheri suggested and start whining at him about it. 
