Can alcohol extraction be used to draw more of the spice flavors out in chai tea concentrate?
Your flavors can be grouped in water soluble and oil soluble. Alcohol now is a mixture - some oil soluble flavors are also soluble in alcohol. These are phenylpropanoids, like Coumarin or all flavors that are themselves based on alcohol, like Hexanol. Alcohol is not a better extractor for flavors, just one with shared properties of water and oil, without covering the whole range!

Now we get to the core of your question: 

Those flavors, that are dissolved in alcohol/oil, are much more stable in alcohol/oil than in water. What you smell during brewing are actually oil soluble flavors that went: "I'd rather dissolve in air than water." When you use boiling water, you are losing flavor that could have been extracted with alcohol.

In order to pull most flavors out of the ingredients, you should therefore first extract most flavors with alcohol and then use boiling water. Also, there is no reason to not use fat/oil, too. While milk is unstable, fat itself is very, very stable. If you ever get one of those Asian cup noodles, you will notice that there is a small packet with fat inside together with dried spices. The fat is not there to increase the nutritional value, but contains the oil soluble flavors.