Looking through bluez:audio/telephone-maemo.c from the SDK also reveals interesting features, such as:

• Inbound voice calls
• Conference calling
• GSM, GPRS, EDGE and HSPA support
• and lots of other little bibbly bobs

Whether all of these would appear in the "Maemo 5 lead device" (aka RX-51), we don't know. But companies generally dislike writing code which is never used :-)