Actually, in my case the error code displayed by the other scanners (P0410) is generic. This code is listed in the manual that came with my scanner. So in this case it is not a proprietary code, and the scanner should detect it, IMO.

Anyway, here's another fun OBD II related story. I live in Connecticut. They recently started a revamped state emissions control testing system. Turns out, for cars new enough to be equipped with OBD, all they do is plug in a scanner to see if there are any error codes. No actual emissions are tested !! I am sure there are many potential problems that would increase emissions, but not be picked up by OBDII.