I wouldn't, since you're going to use some of the water in the tea to digest the tea part, which makes it kind of hard to figure out how much actual water you're getting.

On the other hand, the 64oz of water/day thing is assumed to include water from foods and beverages, so if you're not feeling dehydrated, then say screw it and count the tea.

Just. A few days into using MFP, so please excuse the noddy question. When measuring water intake what is a "cup". I am recording cups (1, 2,3 .etc) but in actuality each so called cup is a 250ml glass of water.

Me personally, if I am not drinking water am drinking unsweetened iced tea. I was told by my doctor that it will give me my water intake of the 64 oz goal and give my body the caffiene that it needs. I am not sure if that truly answers your question, but essentally, tea is flavored water, which I assume would be the same as the flavor packets or Mio that you put in water bottles without all of the sugar. My wife "does not like the taste of water" so she drinks iced tea, she has lost 60 lbs so far using tea instead of water.

Are you drinking herbal tea or decaffeinated black tea? Teas and coffees, whether decaffeinated or not, act as a diuretic, which expel water from your body and dehydrate you. Good rule of thumb is for every ounce of caffeinated or decaffeinated beverage, take in one ounce of regular water. At my desk I have a water cup with fluid ounces marked on the side and a coffee cup that is 12 ounces. This helps me do the math and stay hydrated.
Another important factor to remember is that water aids in the digestive process as well as helping your cells move things around your body. The better hydrated you are, the quicker your body can metabolize your food and the more energy you will have. It also means that your body will be able to break down fats into energy better (YAY)!
If you have a problem with the flavor of water, consider getting a Britta filter. Works WONDERS for our nasty tap down here in Arizona.