So my approach allows you to do this in interface builder. What you do is create 'spacer views' that you have set to match heights equally. Then add top and bottom constraints to the labels (see the screenshot).
More specifically, I have a top constraint on 'Spacer View 1' to superview with a height constraint of lower priority than 1000 and with Height Equals to all of the other 'spacer views'. 'Spacer View 4' has a bottom space constraint to superview. Each label has a respective top and bottom constraints to its nearest 'spacer views'.
Note: Be sure you DON'T have extra top/bottom space constraints on your labels to superview; just the ones to the 'space views'. This will be satisfiable since the top and bottom constraints are on 'Space View 1' and 'Spacer View 4' respectively.
Duh 1: I duplicated my view and merely put it in landscape mode so you could see that it worked.
Duh 2: The 'spacer views' could have been transparent.
Duh 3: This approach could be applied horizontally.