Here is someone who compared his music files in two streams. This is not evidence, but I think it will be helpful.
Qobuz is better. It caters to the group with the ears and equipment to hear what they are paying for. Everyone I know who has Qobuz has upgraded to external DAC’s and better headphones because of the quality.
forum.wiimhome.com
Here, this is good evidence that Amazon Music and Qobuz use the same streams, and rightly so, the author raises the question of whether this implies being Bit Perfect.
However, the conclusion they arrive at is rather weak: you don't need the manufacturer's consent to alter the timbre.
If that were the case, all radio stations, television networks, nightclubs, and so on would get into trouble.
The only thing we can say about that evidence, though very interesting, is that there is likely a common source that the major lossless streaming services rely on.
But nothing guarantees that this, in turn, is identical to the masters.
In fact, it's unlikely to be true because typical playback devices for physical media and streaming are different, and the parameters are calibrated to the device type.
So, a FLAC obtained, perhaps, through ripping a CD could very well have different characteristics from the one intended for streaming.
An indication of this is that there are often versions for streaming that are not available on physical media.
