not too sure, the sony pulse mag doens't say anything, and the sales guy said it's IR, but I then asked if it's mounted on the right of the steering column (NZ cars are right hand drive)how is the head gonna pick up the signal, he said oh, errr... it just does.
So this lead me to beleive that it's possibly RF, also he stated that it only works on the new head units, so this confirms it since the older ones were all IR.