I'm sure that I am alone in this, but I disagree with you on this. What most of us call an extended warranty is not a warranty; it is a Vehicle Service Contract and they are very specific in their terms. Every VSC I have seen specifies that they have the right to use a part of a Like, Kind, and Quality. This means that the donor vehicle should not be older than, or have more miles than the vehicle receiving the part. One of the biggest suppliers of used parts (having purchased Keystone) is even called LKQ and is publically traded.
I am sure you can understand why they specify the right to use an LKQ part. If an engine goes out on a six year old vehicle with 75,000 miles on it, do you expect them to put in a new engine? Drop $5K on a Jasper reman? In order for them to do that, the price of the VSC would be priced so astronomically that no one would buy one. How much would your car insurance cost if replacement value equaled the price of a brand new car? How much would your health insurance cost if the insurance company had to pay whatever the doctor wanted to charge, rather than negotiated prices?
As someone who advertises that I accept "Extended Warranties", I am OK with them supplying their parts. It does not "compromise my integrity". I am not the one insisting on using a used part, and I am not the one paying for the repairs. My job is to make sure that the supplied part is in good working order. If I install it and it does not work properly, I call the insurance company, have them send another one, and rebill them for the labor and power steeing fluid. Remember, the customer is the one who entered into an agreement with the insurance company. It is their obligation to have read and understood the terms of the contract. But they don't. They hear "bumper to bumper" from Plaid Coat Charlie at the car lot, and that's all they hear. Take personal responsibility for signing a contract without first reading it? Surely, you jest!
Anytime an insurance company wants to supply an LKQ part, I always explain the options to a customer. In the case of a rack and pinion, I will tell the customer that their VSC will assist with $---.-- for the part, or they will supply a used one off of a vehicle with less miles than theirs, or I can install a new or remanufactured one if they would like to pay the difference. Very seldom have I had a customer choose to pay the difference. In almost every case they choose to have the used, LKQ part installed.
I know what to expect from the insurance companies and I treat it like a game. If a customer tells me they have an extended warranty, when I blink, you hear an old timey cash register sound. I read their contract, and then go over the car "bumper to bumper" looking for things that the VSC will cover. Oil pan gasket leaking and the VSC has seal and gasket coverage? I will charge for the gasket, the RTV, the oil, labor and diagnostic time. Rack and pinion leaking and they want to supply the rack? No problem. Labor, PS fluid, and a half hour diag, thank you very much.
I always tell the customer that the insurance companies job is to make sure that they spend as little on car repairs as possible and that my job is to make sure that they spend as much on car repairs as possible so that the customer gets the full value of what they spent on their VSC. The insurance companies are constantly sending inspectors out, but I stand behind every repair that we call in and we have a very low decline rate. That is how I make my customers happy and don't compromise my integrity.