CPO covers drivetrain and other components. Look at the docs for exactly what, but engine, tranny, injectors, etc. are covered. A few of my injectors were replaced under CPO.
Also if you have a CPO car, DO NOT BUY THE EXTENDED MAINT!!!!
It is a gross waste of cash. I bought it and since you are stuck with 15K oil changes and for CPO they make sure the brakes are good. The chances are that you will never go through the $2K that the maint costs. You are better off putting the $2K in the bank and paying for it out of pocket. IMHO.
THis is from a gu who has forked over the $2K and probably will never see a decent turn.