Awesomely, this chip has an open datasheet
Hopefully the downloaded ROM supports the low level requirements for the other profiles. If not, downloading a replacement doesn't look too hard.
No detailed information so far.
However it is believed that out of a normal Bluetooth stack, all protocols up to but not including HCI are implemented on-chip in ROM. HCI and L2CAP seem to be handled (however badly) by the iPhone driver software.
Main article: Bluetooth