I just got a new key being made (but I live in China so not sure it will be super helpful)
Anyway, the guy did it in about two hours, he said it was the same system as used on Ferrari.
In order to program the key, he had to take out the whole fusebox that is located near the steering wheel. On the backside of this fusebox there is the main body computer, which apparently controls the key system.
He removed its whole mainboard and he soldered some wires directly onto its main chip's legs.
After that he connected to the chip using some kind of interface and loaded some files. He was following a tutorial on his smartphone so I guess this is fairly common here in China.
Anyway, after that he carved the key using a mini portable fully automated CNC milling machine that was super fun to watch.
Then he reinstalled the fuse box and put the key in the ignition.
Last, he used some kind of wire loop in order to sniff the signal coming to/from the transponder, then he used a special tablet connected to the OBD port, did a few operations and it was done.
The key is fully functional, just like an original one. It can control all the remote functions and start the engine.
That cost me 100 euro for everything.