In the end, its the insurance company that makes the decision as to which parts are used
Thecshop can say all they want to save face, but if a new part is being used in place of a lkq or a/m part, that was the decision of the adjuster to maintain customer service.

I was under the impression the customer has the option of requiring oem parts and insurance company by law has to comply.

That is incorrect. In many instances, depending on the policy, the customer has the change to purchase an OE endorsement that allows them to have only OE parts on the vehicle. If the policy doesn't have that endorsement, the insurance company can use LKQ and A/M parts if available, and only if they are insurance quality. If for any reason the LKQ part or A/M part that was sourced isn't insurance quality, than the next step is the usage of OEM parts.

It is very important that you read your policy and have detailed conversation with your insurance agent.

Just wantd to update the thread, it turned out that the 'backorder part' wasn't needed at all, (or maybe he was just making all of this up to buy more time for the repair), and I got my car back as per the original scheduled estimate (+ 1 day since it snowed here). Life is back to normal now.

It was unfortunate I hit my car 3 weeks into buying it, and that too because some girl was running her light - although I know its impossible to buy that when I'm the one in a red sports car :)