ah yeah the m4r trick. Still a hoop to jump through, even if it's an easy one. OBEX could solve it, but that's one of the minor points and not a particularly huge one for me personally (I usually hate hearing phones ring period rely on simple soft beeps or just vibrate).
Wouldn't surprise me if there are some glitches in bluetooth implementation, but that's a different than deliberate subterfuge, carrier-initiated or no.