Now, some of that reputation is based on the fact AA is religious based (Through NOT tied in with any one religion, just a belief in God and to look to God for support in one's fight against Alcoholism) and that religious dogma is viewed by many people as needed to help someone over come alcoholism. On the other hand many judges just like what they have seen when it comes to people who had gone through AA (and stay in AA after they dried out).
One of the chief reason AA is so successful is it does two things quite well, first is get people together who have something in common (one of the characteristics of being human is we talk to each other all the time about things we have in common, if you have nothing in common you do NOT talk and do NOT becomes friends). An example of this is from the 1800s, two Irish groups, one from Northern Ireland of mixed Catholic and Protestants and the other from Southern Ireland, all Catholic, were building two different railroads near each other. When one groups of workers of these two groups meet another group of workers from the other, it almost always ended up in a fight for neither group had anything in common with the other to talk about. This conflict lasted for weeks, if not months, then it finally broke down when both groups were off work and in the same town at the same time. This resulted into a near riot as the two groups went after each other do to all the tension that had been building up between the two groups for months. This riot was broken up, but a funny thing happened afterward, whenever members of each group meet each other afterward sooner or later the talk ended up in what they did during the big riot. No more fights occurred for finally the two groups had something in common to talk about, what any of them did during the big fight.
AA is working on the same principal, the AA get people together who have something in common, they history of alcohol abuse. This is the common topic the members have in common, it gives them something to talk about and they talk about avoiding alcohol abuse. This lead to the second and related item AA does, it provides a new network of friends for the ex-alcoholic. People deal with people like themselves, people they have something in common with. Alcoholics (and drug addicts) tend to have friends who are alcoholic and drug addicts. The ex-alcoholic needs new friends, but people develop friendships with people they can talk to given what they have in common. In the above example, the railroad workers had nothing in common till they had the big fight, then they could talk to each about what they had in common, what they did in the big fight. The same with ex-alcoholics and the AA, it provides a place for ex-alcoholics can meet other ex-alcoholics and develop new friends. Only with the development of new friends can one drop your old friends, and in the case of AA members the old friends are active alcoholics (or even causal drinkers) with whom the ex-alcoholic had in common was the use and abuse of alcohol.
Thus AA does two things quite well, first it provides a way to get new friends (based on the fact the ex-alcoholics have something in common, they abuse of alcohol) AND a mechanism to DROP old friends (Friends the ex-alcoholic needs to drop for they were friends do to the fact what they had in common was the abuse of alcohol).
AA has a better reputation on this score then anyone else, mostly because it is a voluntary group (some people are court ordered to join, but the AA does NOT enforce such membership through the AA does give out certificates of attendance). I suspect other groups can provide a similar program, but from what I have heard, no one has the record of the AA. The AA is constantly attacked do to its emphasis on religion, but the AA does NOT force people to join it.
Now, a lot of Judges have seen the help the AA has does since it was founded in the 1930s and will order people to go to AA meetings hoping it will help. I suspect the same thing in going on in this case, the probation officer has seen good things out of AA and thus have more faith in AA in helping the Alcoholic then any other group.
Just pointing out that the impression of many people in the field, i.e. people who are dealing with alcoholic in the legal field, is that the AA provides a very good service and for that reason is their first choice. They will consider others, but the person on probation has to come up with the program AND hopefully a program near their home (AA has meetings almost any where almost every day of the week, and thus such meetings can fit almost anyone's schedule, another factor in any Judge/Probation officers outlook when it comes to getting someone "help" for their addiction.
For more on the AA:
http://www.aa.org/?Media=PlayFlash