I think it can only be removed via a system update which is country specific.
I have already asked my dealer and he advised that it was to comply with Australian standards requirements. My previous car was an e39 540 and I could remove the startup screen with a modified nav system operating disk.
E39 e46 and X5 used I-Bus for nav and entertainment and this has been hacked by quite a few programmers to achieve things such as customisation removal of start up screen.
E90 and E92 use MOST bus for nav and entertaimenment and I think this is more secure and has not been hacked as yet.