After hours of hacking around, it turns out the dash gets interpolated! Quotes are needed.
<i class="icon-home" ng-class="{'icon-white': someBooleanValue}">
UPDATE:
In older versions of Angular, using a backslash also does the trick, but not in the newer versions.
<i class="icon-home" ng-class="{icon\-white: someBooleanValue}">
The former is probably preferred, since you can more easily search for it in your favorite editor.