Transfer AppleCare Plus to iPhone 5

I bought a used iPhone 4S 64GB on eBay with AppleCare Plus included. It shows on the Apple site when I sign in to my AppleID. Does that make it officially in my name?

I am curious because I may trade in my 4S 64GB at the Sprint Store for an iPhone 5 64GB. They offer $300 out right off the purchase price and I just pay the delta of $99. I know I could get more by seeking out right on eBay but consider most don't go for the 64GB model and after fees & shipping, I don't think it'll amount to enough for the hassle.

I read that you can't transfer ACP to another phone but Apple will prorate a refund. Does anyone know how that works toward a new ACP or if you can transfer the remainder to the new iPhone?

Thanks!