Don't know if anyone else has tried this yet, but I just fought a custom battle in RTW after installing BI.
It was on grassy flatlands, with 6 Macedonian Phalanx pikemen defending against 6 Seleucid Phalanx pikemen. The Seleucids were under AI control, but I didn't alter the deployment of the Macedonians or issue any orders to them throughout the battle.
https://img179.imageshack.us/img179/3917/00066fl.th.gif
Setup
https://img179.imageshack.us/img179/...ears0es.th.gif
It dropped spears as it approached, and began obviously pairing off against my units.
https://img179.imageshack.us/img179/...good8jq.th.gif
Looking Good
https://img179.imageshack.us/img179/...last9xa.th.gif
I've been waiting years to see this!
https://img179.imageshack.us/img179/...ight9gn.th.gif
Phalanxes fighting properly!
The Macedonians won, but suffered nearly 50% casualties (in my excitement I forgot to screenshot the final score) so Phalanxes are still a defensive formation. I might go see how it behaves when theirs cavalry and missile troops about now.