Easiest way might be to build a standard Tamiya chassis and then mount the cab and body from the Bruder truck onto it, rather than try to convert the Bruder chassis to RC. There's a YouTube vid of somebody who did something similar with a Bruder cement truck.
http://www.youtube.com/watch?v=v9Wr7cnqn6A
Looks like the only mod to the stock Tamiya chassis is the use of super single rear wheels (to get the width to match the bruder body) instead of dual rims, but these are standard parts from the reefer of container trailer which include the hex shape insert for drive transmission.
Plus of course you'll need some form of screw drive for the tipper bed...