From my research, this looks like it can be enabled with the following AT command (if you can get your Pre3 into DUN mode and send AT commands to it):
0 - Accept from any mid in list
1 - Accept from any mid not in the list
For instance, to add CB channel 50, I would do this:
For channels 50 and 0:
And, to see which channels the device is listening to:
I haven't tested this yet, though... Not sure if it will work, and if it does, how the device will respond.