Our Friends over at XDA-Developers have been able to install an early build of Android P on the Huawei Mate 10 Pro. Currently, the Android P developer preview is only available for the Google Pixel, Pixel XL, Pixel 2, Pixel 2 XL, and technically the Huawei Watch 2 for Wear OS based on Android P.
We initially assumed that a ROM developer was able to port Android P over via Project Treble, which has made it easier to port a vanilla Android ROM to smartphones that come with heavily modified OEM skins like the Galaxy S9. However, it turns out that this is an Android P build with EMUI for the Chinese version of the Mate 10.
First, a Huawei device ROM service called Funky Huawei is needed to rebrand the Mate 10 Pro to a Chinese Mate 10. Then, the built was able to be installed to the Mate 10 Pro, also using the Funky Huawei service.
Source: XDA Developers
The build is far from final and doesnt offer things like Material Design 2 or new iPhone X-style gesture navigation. Although the EMUI version is listed as 8.2, the build is indeed Android P since the build number is listed at 9.0 and the Android Easter Egg is for Android P. Otherwise, apps that are in the build were built with the Android P SDK.
Check out the source link to see a more detailed explanation about the Android P build for the Mate 10 Pro.