I have used SE & Parrot bluetooth kits with my RNS-D, no problems, I had to buy the mute kit for the SE HCB-30 kit, but the Parrot CK3300 wired straight in.
That is basically what this guy has done in a B5, but you do not need to do anything that complicated, just wire the TEL MUTE, TEL + & TEL - leads to the RNS-D and that should be it, you can also get Live, switched live and gnd from the back of the RNS-E harness.
The RNS-D will display telephone when on a call. Also the cluster will show TELEPHONE.
Hope that helps.