On the start stop tech I read and saw a picture of a 4 Cly that used some that looked like Starter/Alternator. Was supposed to spin the engine fast enough to take off and start the engine at the same time. Similar way when someone crank the engine with the clutch engaged. The drive belt looks like some that came from a Harley Davidson.
One thing that people need to be aware of Caddy engines, they are too expensive to repair. I know some people with Caddies, specially with the Northstar V8. They have some maintenance unfriendly engines.
But knowing GM, these engines might be only for Cadillac. Is the only division that I know that makes its own engines and does not share them. A Caddy "shared engine" was the
Oldsmobile Shortstar that came in a form of a 3.5 V6 (LX5) and 4.0L V8 (L47) Aurora engine.