Although I am very much 100% retired from OpenTTD development, I have a big interest in finish up the NoAI of OpenTTD. The main problem I had in the past, is that there was no user-group which tested the function we created, and gave advise on functions they needed and used. Therefor, it was impossible to continue this API, as I had no idea which direction to go.
That said, I am willing to help you out finishing the NoAI to which ever extend you need for such an AI challenge, if you can help me by telling what you need exactly. Of course this doesn't need to be done at once, and can change in time, but the feedback is very much critical for any success of NoAI.
If you are interested, please drop me an email at truelight at openttd.org, or visit me at IRC (irc.oftc.net, nickname TrueBrain, I am online, just not in any normal channel


Also I would like to ask, while looking into NoAI and creating AIs, to update and add things to the AI part of the wiki: http://wiki.openttd.org/index.php/AI:Main_Page. This is also a critical part to make NoAI any success.
To give some addition info: there is a (small) list of things that needs to be done in NoAI here: http://wiki.openttd.org/index.php/AI:TODO