Of the new maps, Trackside Tragedy is very different from the final version
The new enemies are not there yet, so we got Pig Cops instead of the new pigs, etc.
Trackside Tragedy is filled with Recon cars, obviously a placeholder for this enemy:
Even if they couldn't make the new enemy work, it's a real shame they removed the Recon cars, the map was clearly designed to fight them.
I read some article that the game would have pigs dressed like Lara Croft and with the Reservoir Dogs suits. Since the enemies were placeholders, I'm guessing they couldn't make them in time and the Pig-in-a-Dress was just put in Nightmare Zone. I'm just guessing, but the Pig-in-a-Dress must have been intended to serve as waitresses in the café from Pulp Fiction. The pigs in a suit would also fit Alien Rendezvous, which would have made the X-Files reference more clear.
Images:
https://imgur.com/a/smMyG7I