In response to some posters:

1. Out of province cars will get billed. This includes you. If you don't pay, most states/provinces have reciprocal agreements that will cause you trouble at license renewal time.

2. You are free to switch your transponder between vehicles, as long as you don't mix up truck and car transponders. If you bring a transponder with you in a rental car, the transponder will be billed and the rental agency will never know that you took the 407.