Thanks to allot of internet research I became brave enough to deal with the new experience of a rear brake job with the added interference of the on board computer. I have an 09 XC70 t6 and it turned out to be really easy to do the job without buying a release computer tool or bringing it to the dealer.
Basically, take the wheel down to the old brake pads out and if you're changing the rotor take the caliper holder off too. On the top of the ebrake motor is the electrical plug in connection clip that removes pretty easily if you look closely at how it comes apart. This will reveal on the inside of the connection clip on the motor two prong terminals. I got out my 12 volt booster charger and connected a smaller wire to each of the clunky clamp ends to make it easier to contact the terminals on the connection plug in. If you do positive on the left and negative on the right terminal the motor will retract and allow the piston to be pushed back inward. You have to push the piston with a tool that will give you enough leverage to push it in. It shouldn't be hard to push in. You don't need to turn the piston. If it doesn't want to go in you haven't retracted the motor enough. Reversing the two wires will make the motor push out it's piston and apply the brake. Keep the connection together just long enough so it allows the piston to go in far enough to allow the caliper to go over both pads. Make sure you don't turn the car on at any time with the connection plug in clips removed because it will code out on you and take nearly 100 miles of annoying chiming telling you the ebrake needs service or isn't fully retracted. Do the same for the other side making sure both connection clips are back in place before starting the car or moving the ebrake handle. Start it up and everything should be fine. If for some reason you get a warning that the brake is in need of service or not retracted, make sure that the car moves freely then drive it for a mile or so. Stop and check to see if the rotors are warm but not super hot. If they are all warm you're fine and the annoying chiming will stop after 75 miles of driving.