For 1.5 years I have been going back and forth with my dealer over brake squealing. They say the service bulletin isn't applicable in Australia.

It only occurs when driving slowly and coming to a slow, full stop.

I have paid for new brake pads and rotors and the issue was still unfixed.

Last month, and without my approval, they swapped my brakes with a demo CLA to "test" whether it would fix it. Should I be worried that 1) They have put used parts on my vehicle and 2) It's a different model?

The squealing has stopped but now I have a metal sound that makes me think the parts don't correctly fit.

 

I always find it very interesting and a bit concerning that the majority of service bulletins for the cars are somehow not applicable in Australia, it is as if cars sent to Australia are much better built. Personally I think it is the soft consumer laws that allow companies to get away with it here. Eg the wind noise bulletin is somehow not included in the Australian market, along with the squeaky suspension.
Thankfully this hasn't happened on my C class, I do have this problem on my E class but it isn't that bad so I just live with it.
That is a big no IMO, I thought the CLA runs on single caliper fronts? Wonder how they all fit together.