If they all died in the battle, only a few could be resurrected in the itzama. And if it was a draw, I would expect each of the combatants would have their own amazons and nahuals resurrect, as they only defect to the winning side. In a draw there is no winner.
Amazon is correct 
Nahuals give information about troops coming and going out of a city. For how long does a nahual supply this information?
When you get a report from Nahuals, what you get is a "snapshot" of the exact moment the Nahual arrived at the city. So Nahuals don't provide information for a particular period of time, but rather static captures of a moment. So in other words, you need to send more nahuals if you want to be updated of your rival status.
Also can nahuals be detected and killed?
Nahuals cannot be killed on a espionage mission, but if you are on the receiving end, you can hide your troops from them, See this guide for details (scroll down to the Nahual section). You do get an notification if someone has sent Nahuals your way, though, so you will at least know.
And lastly suppose i am trying to spy a person with a nahual who has sent his troops to his alliance member's tambo. Will that show in Nahuals report?
Unfortunately not, Nahuals currently do not support troops that are stationed in Tambos. This is not set in stone, it could change in the future.
