I'm not sure if this helps but I tried a similar experiment. I don't even like BT but I wanted to prepare for a possible time I might need to tether to my laptop (I don't own a cell phone). I found that PAN works paired to my Dell Inspiron and the internal 355 BT. We're connecting to the "Network Access" service on the laptop. On the Dell I created a bridge between the BT LAN Access Server Driver and the Ethernet interface that the laptop has LAN access (in this case WiFI, silly but I wanted to make it work WiFI and Ethernet). No MAC addresses to fool with or file edits.

Get paired up with the Dell and then do a Change Connection from the NIT and pick Bluetooth-PAN. At the list choose your laptop which should popup a pairing or authentication screen on the laptop. At this point the WiFI should go off and you are tethered to the laptop via BT. This worked for me.

One caveat on mine is that the NIT will reboot each time I change bewteen BT-PAN and WiFI. I didn't get this working on other PCs but the internal Dell BT seems to work better overall than any other I tried. Did I mention that I hate Bluetooth??