The researchers for this mod have probably covered everything, but I thought id point this out:
http://muse.jhu.edu/demo/journal_of_...7.1boesche.pdf
A journal article on Chanakya's political/military 'Arthashastra', which amongst other things, included a detailed desciption of Pataliputra, i.e. the dimensions of the city, the size and depth of the moat, the city walls (which were wooden due to lack of stone in the Gangeletic plain), the number of towers and gates.
It is described as the largest city in the world at the time, the population of the Mauryan Empire is given at 50 million, and the city of Pataliputra was twice the size of Rome under Marcus Aurelius. It very much confirms that India was already heavily populated, and urbanised, at the time of the mod - which unfortunatly dosent bode well for the Alexander expansion.
Also, stuff which I had seen before in the biographical account of Chandragupta Maurya, such as the size and disposition of the Mauryan army are included. Since your mod is set during the rule of Bindusara, accounts of Chandragupta and Chanakya of course are usefull.