Those T-routes usually circumscribe class Bravo airspace (like in your example). I always thought they put MAAs because they wanted to keep people on those routes while not having them get in the way of the arrivals and departures from the main airport. There is one around ORD that also has MAAs and I think it is for the same reason. MAAs for victor airways usually have to do with signal interference and I dont think that is the case here. I could be wrong though.