Nup, it's a different system on the R-class from the SL where COMAND can play DVD's. From what I've been told, you have to get a DVD player to plug in.
I mailed
steve@MBenzNL.com and was told:-
"you will need an additional aftermarket device that gets mounted in between the TV tuner and DVD comand. This device will enable TV while in motion, because the DVD comands in the R-class (and W164 M-class, and facelifted W203s, W209s, A and B-classes) can NOT play movie DVDs by itself and can NOT be versioncoded through stardiagnose for TV / DVD while in motion. The DVD comands in these MB models can't be compared to the ones that are being installed in your facelifted SL (or the W211, W219, R171 for instance) that all have a SEPARATE navigation drive that can be installed in the boot.
The aftermarket device for TV / DVD while in motion can be offered for Euro 200 including shipment per International Priority Post and including 19% Dutch VAT."
You could try mailing Steve for more info, I'm sure he wouldn't mind.