Yes, every Polo has a BCM, thats right!
But if you look at the VW Workshop Program (ETKA), you can see that the 2012 Polo has a lot of different BCM, so the Blue Motion Polo an Polo with Xenon has other ones with other electronical connection!
And if you look in the other VW Workshop Program (ELSA), you can see that there are different on-board power supply wiring diagrams for normal Polo with H4, normal Polo with H7, Polo with Blue Motion and polo with Xenon heasdlights!
And if you look at these wiring diagrams, you can see, that the light control between a normal Polo an Polo with Blue Motion or Xenon is very different!
At the normal Polo the light change is controlled by a simple relay (Not BCM!) which is controlled by the light switch.
But at the Blue Motion and Xenon Polo, the light control wiring is other, without relay, but with wiring across the BCM like you know it.
In an other panel, some User tested it! Codings that works on a Blue Motion or Xenon Polo is not invariably the case that it works on a normal Polo! Particularly light codings.