Is this the shield that you are talking about : http://www.arduino.org/products/tinkerkit/arduino-tinkerkit-braccio . We have not tried it but it does look like it should work with the Arduberry.
You should be a bit careful about the power supply though. The tech specs say that you need 5V at 5A which is a lot. I am not sure if it is shared with the Arduino, if it is then it would be shared with the Pi too. Servo's tend to generate a lot of noise in the power channel which could make you Pi run a bit unstably. So this project would be more like, proceed on your own risk.
You should also have a look at the pivotpi here that we sell for the Raspberry Pi: https://www.dexterindustries.com/pivotpi/ which you can use to control the servo motors with the Braccio. Might make it easier for you to control the Arm from Pi itself and we have a library in C and Scratch too.