You can get this feature at their lowest end model of that series (CA49), though it may lack some other aspects of the resonance modeling that they reserve for higher end models. I believe almost all digitals starting at $2000 across the board have this feature, and the limiting factor that'll hold you back from hearing it all at the lower end of the price range is the audio setup that comes with the keyboard.

I remember discovering this feature when I held down all keys from A0 through E1 (without sounding them), depressed the sostenuto pedal, and then played a bunch of other keys.