Marcin,
once again congratulations on your progress, and thanks for the update.
I wish I could actually jump in and also do some work on the non-GSM related Linux drivers, but I'm currently too busy with other projects.
However, I still intend to work on the GSM part of the MTK chipsets, probably from January 2011 onwards. I've already spent quite some time reading thorugh the various MT623x and MT6139/6140 data sheets and other documentation that we found, and I believe I have a pretty good idea how everything works - with the exception of the details of the DSP/ARM interface that is not documented anywhere.
Regards, Harald