I just received my new 9070 shifting group, and could not wait more to put them on my bike. After I connect every component with firmly plugged wire, I just found there is no response from the group with battery installed. So I called Shimano support, and they asked for my battery mount(the dealer sold me a SM-BMR1 Short) info after hearing my description of what was going on.They said that probably SM-BMR1 mounts did't support 9070 Di2 group when they come out from factory line, that the BMR1 was made for 6770 and needed a firmware update performed to make them compatible. However such update could not be performed with a SM-BCR2 internal battery charger as I used to update other components' firmware. The EW90A/B junction kit just doesn't recognize un-updated BMR1 mounts so no go update via EW90A/B with BCR2. I will ship my mount to shimano tech center to deal with it because local shimano dealers don't have PCE1 to perform the update. That's all what I have been told after several rounds of calls. I don't know if it's really the fault with BMR1 that prevent the whole group from starting until I get the updated one. So for those who are buying their new 9070s, just make sure your dealer sells you a BMR2, BTR2 or an updated BMR1

It is the BMR-1. I was unable to update mine with the BCR-2 as well. The remainder of my 6770 group updated fine. It's weird but same thing for me.