If you have 2+ people, you can use the MnPass lanes without a transponder. The special lanes seem to be labeled for this. If you have a current MnPass transponder, you need to turn if off when you have 2+ occupants in the vehicle.

I have EZ-Pass and MnPass both mounted on my windshield, so I'm wondering whether I need to temporarily (during the transition) or permanently turn off the MnPass transponder.

MnPass fees are congestion based, varying from twenty-five cents to eight dollars, and on some roads, usage of MnPass lanes is free (for everyone) at off peak times. During the free times, the MnPass lanes can be much faster, but most drivers don't seem to realize that they can be used despite the prominent signs. AFAIK other states in EZ-Pass don't do congestion based tolls, but I've only used EZ-Pass in four states so far.

My EZ-Pass transponder from Illinois doesn't seem to have an on/off switch for vehicles having 2+ people. At least in Illinois, I seem to be charged a fixed price for using each piece of road.

Another difference is that in Illinois, Indiana, Ohio, and Pennsylvania, my EZ-Pass privileges seem to involve the use of roads that are always tollways and have some alternative mechanism to pay, although the Ohio system is bad in that you still wait in line behind cars paying cash, versus the Illinois system that has a lane or two set up for vehicles without EZ-Pass with everyone else being encourages to use the other lanes without slowing down for the tollgate. In MN, if you aren't a carpool and don't have MnPass, you *cannot* use MnPass lanes without risking a ticket; there's no option like in Illinois to pay online later or (currently not at any toll plazas AFAIK, but this was true in the past at major toll plazas) to pay by cash or credit card.