If you look at the cars playset gameplay from gamespot You'll see a cutscene were mater is talking to ramone and mater's voice and holly's voice is well heard which probably confirms they will have the orginal actors voice the characters or other actors replacing them. like jim hanks replacing tom hanks etc.
The public is in danger! My evening's in danger! You tell me where my suit is, woman! We are talking about the greater good! 'Greater good?' I am your wife! I'm the greatest *good* you are ever gonna get! "