I was at the Belvidere oasis in IL on Saturday. (Dennis Hastert’s 1940 Lincoln is still on display there, but they’ve removed the sign saying it belongs to Hastert.)
My sister had to exchange her old iPass for a new one, and I came along to buy one. (We have shared one for years, but at times getting it back and forth between vehicles was a PITA.)
At the end I asked the clerk, “We’re going back up the toll way and we’ll have 2 iPasses in the same car. Are both accounts going to be charged for the tolls?”
The clerk “Not with this” as he hands me a square of aluminum foil, probably about 4"x 4", enough to completely wrap the iPass. “They can’t be read through the foil.”
That’s what my crazy neighbor used to say about his brain. 
Yeah, when we got our FastPasses, they came with a thick conductive-plastic bag to put them in and keep them from being accidentally read. But your official government issue tin foil beats that.
That’s what they WANT you to believe!
“Such a lovely name for such an ugly place to go”
Reminds me of a news item (or maybe it was a sub plot in a TV show??) about someone who mailed their pass back when they were moving from the area. The mail truck(s) drove thru several toll plazas and the mailed pass was charged as well. The guy was on the hook for the charges.
And as it happens, I have one of those magical plastic bags right next to me holding my daughter’s EZPass. I was going to turn it in for her since she moved to FL, but apparently, it’s hers forever. So when the clerk gave it back to me, she bagged it. I didn’t have to go thru the plaza, so it wasn’t an issue, but now I know.
In IL, the iPass continues to be the property of the state. But if I turn it in, I get a $10 deposit back. Or so they claim.