Nexus OTAs are a pretty big deal, even when they're not official releases. With that said, here are the OTA links that we have for the Android Developer Preview 3, build MPA44I. If the link for your device isn't shown, it means we don't have it yet. We'll update this post as links come in. As with any OTA, these are intended to be flashed in stock recovery on a completely stock, unmodified MPZ79M system. If you have modified the system (root, Xposed, etc.), these won't work. In that case, you should flash the factory images instead.
The Pixel Launcher from the Pixel 3 brings the Assistant button back, forces adaptive icons on all apps, and more [APK Download]
Which Pixel 3 features are coming to older Pixel phones (and which will remain exclusive)
[Update x2: Statement] The Pixel 3 is the first Verizon LTE Android phone to be SIM locked in a decade, and that'll be a problem for some