Hi all!
In case you're interested, there seems to be a public project on code.google.com that contains the build environment and baseband firmware sdk from mediatek:
svn checkout http://mobile-phone-mtk-project.googlecode.com/svn mtk-project
Please note that I don't know about the legality of this. However, it is distributed on a public server/service without any kind of authentication...
Regards, Harald