Yes, you can do this solely in interface builder and without writing code - the one caveat is that you are resizing the label instead of distributing whitespace. In this case, align Label 2's X and Y to the superview so it is fixed in the center. Then set label 1's vertical space to the superview and to label 2 to the standard, repeat for label 3. After setting label 2 the easiest way to set label 1 and 3 is to resize them until they snap.
Here is the horizontal display, note that the vertical space between label 1 and 2 is set to standard:
And here is the portrait version:
I realize they are not absolutely 100% equally spaced between the baselines due to the difference between the standard space between labels and the standard space to the superview. If that bothers you, set the size to 0 instead of standard