All service contracts are negotiable--what is not negotiable after the contract goes into effect is the service provided.
OEM-what ever company, will specify that your vehicle is repaired with NEW, ORIGINAL EQUIPMENT MANUFACTURER parts.
As a service manager in DiamlerChrysler shop, I have seen many "recycled" (junk yard) engines and transmission installed in vehicles covered by third party service contracts--Why-that is what the Service Contract Provider mandated. If the owner wanted OEM-they had to pay the difference. Another little fact is that the third party providers will only pay a given amount for a repair-should the area you reside in or your vehicle fails in has a higher labor rate that is more than what the company will pay--that additional cost is YOURS! OEM contracts can be cancelled by the purchaser for what every reason; sold it, totaled it or just changed their mind. This is not true with some third party providers.
With DiamlerChrysler, we have no option-it is new and it comes from Chrysler. We have an SLK320 Mercedes, and I have a negotiated service contract on it. The selling dealer shaved $300. off the advertised $2300. This is in addition to our 2004 XC 70-which I will purchase a service contract for as well. I also had an OEM service contract on my 1990 Jeep Cherokee--in 1990 the warranty period was 12 months/12,000 miles.
If you are planning to keep you vehicle beyond the normal warranty--it can be a good purchase. It is much like life insurance--You buy it and try as hard as you can to never use it.
The original cost of a product that has any length of life span is very much like the tip of an iceberg--the part that sinks the ship is the huge mass of cold reality below the water line (maintenance and repair).
As the gentleman said earlier--get educated, get smart and get the product you want which includes not getting a service contract if that is your educated decision. I do hope you never have the need for it or life insurance.