Is the Lucerne the same chassis? It does have a similar looking interior, and a Northstar!
Yes, it is. I believe GM calls it the "G" platform. The old Seville, the LeSabre, the Park Avenue, and both generations of the Aurora were all G platform. As you can see from the interior shots of the Lucerne, the console, shifter, and steering wheel are all identical to the new DTS. And all but the outer cover of the instrument panel is probably the same.
I'm I the only one that sees the VW Phaeton in the Lucernes' rear end? And the roof line is yelling Infinit G35 to me.
Also, GM has been putting the front-drive version of the Northstar in versions of the Bonneville too.
The front looks like a widened STS/CTS/SRX, and the rear looks like a Chevy Monte Carlo. The interior looks similar to the Buick but better IMO. What a shame, the DTS was the one Cadillac that had a nice interior.