I have exactly same question.

One of the older devices I have has a traffic transponder in the cable, tiny plastic brick and without it I don't get traffic data (It has never been correct though, but thats whole lotta another issue). Another device I got claims, it has FM receiver of some kind in the device and no such transponder in the cable. So I am wondering the same, what if I use standard charging cable connected to a phone charger? Will it work?