They appear to work on the same frequency. We bought a "Lighting McQueen" and a "Mater", and we thought "Mater" was broken because it would only move sometimes, and wouldn't go where we wanted. We returned it for a "Finn McMissle", and when both kids were trying to use them at the same time, one controller would run both cars. Other times, one car would just sit still, even though the "forward" level was being pressed, then all of a sudden, it would move backward - this happened if the other child move the other car backwards. This was similar to what was happening with "Mater". My husband realized they must be using the same frequency.
This led to a lot of tears...try to explaining radio frequencies to a 3 and 5 year old and why only one of them can use their toy at a time...however, good tools if you are trying to teach "taking turns"