I've got a Nexus 4 which works fine (via bluetooth) for calling and dialling with v5.6 on the old Gen1 Blue & Me in my Bravo (which only has one USB port)..
SMS reading is the only thing that doesn't work (the phone doesn't support Bluetooth MAP - I'm working on fixing that)
On mine I just pair it up, wait a minute for the car to shout welcome at me and ask to copy the phonebook, acknowledge that request on the phone (tick always allow here).. wait a few mins, and can start dialling.
I think the newer B&M systems must be a bit different if you have 2 USB sockets, I cant play music from my phone (if I connect it to USB it doesnt work as the N4 will show only as an MTP device and my B&M doesnt understand it.. works fine with a USB stick in mass storage mode though).. Not sure if you can do this via A2DP over bluetooth on the newer system or not?
if so I expect it will work as the N4 does A2DP fine..
does it work if you say dial and then dictate a number to it rather than trying to use phonebook?? (Say Dial, wait for beep then say: one four seven one, dial, yes)
The biggest problem is the bluetooth on the Nexus is buggy (I've had 3 phones now as Google/LG keep replacing them despite it clearly being a software fault that needs fixing) and sometimes gets stuck Off.. until you reboot the phone.
That problem isn't specific to the car though, and its not your issue if it has connected..