The Nokia 7 plus has been one of the devices supported in Google’s Developer Preview program for Android P from day one, and the device recently received a new DP build, after some complications caused by updates. Why was Nokia 7 plus chosen and not the the 8 Sirocco, 6.1 or Nokia 8 for taking part in Google’s Android P DP program, I don’t know. I can just guess that HMD expects the 7 plus to be the most popular device for developers and Android enthusiasts that are testing Android P.
In China, Nokia phones use Android without Google framework, and HMD is ready to conduct a wider and long term Android P testing for models available there. Via the unofficial NokiBar baidu forum, users were informed that they can register to take part in Android P beta testing for Nokia 6.1, 7, 7 plus and 8 Sirocco. The registration were open from 21st to 24th June, and users had to agree to a NDA (Non-disclosure agreement) before registration.
There is no date given when the Android P beta testing in China starts, but considering registrations are over, it should come “soon”, especially because it was mentioned to be a “long term” testing process.
source: Baidu Nokibar