So let's see what's under the shield! I had to remove the shield, the SIM and SD connectors with my hot air station:

And here's the PCB in all its glory:

The Mediatek chipset requires a very small amount of passive components to work, so the PCB design is quite simple, as it's just a matter of connecting the chipset to the data bus and take care of the antenna connector coupling. Here's the basic public block diagram for the chipset: