You know, the easiest way I've been able to get heights is to email a tenent in the building in question and ask them to forward my message to the building manager. More often than not they will and I'll get my answer, or they will do the research themselves sometimes! I actually got a new building height for my city today, by just doing this method.
The key is to let them knew clearly and consicely that your requesting the heights for hobby purposes or for a project. They are usually more than willing to help you.
Ain't nobody got time for that.