There are no .EMP files, but all of the standard races are in the ZIP, pre-tweaked for P&N.
When you start a game with random empires, they will all show up.
I did not include .EMPs for the "add existing race", but you can create them by simply saving the AI races during a game.
If you wish to add more races you can simply copy their pictures/races/[racename] folder into P&N, and run the
AIPatcher.exe on them.
The AI patcher can convert any race designed for unmodded SE4 into a P&N race.
There is a known problem where AI designs without any extra ability calls will not work, but I've only seen this occur in one race.
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I highly reccommend the TDM modpack. They are very dangerous, even under PBW Versions of P&N.
PS: Be sure to disable quantum reactor techs (resupply tech area) when playing with AIs in a PBW game. Quantum reactors cost $40K, and can easily destroy an AI's economy with one per ship!