It looks like being an all-in Project Fi customer has some benefits. It turns out Project Fi customers with damaged phones are offered a one-time replacement of their Nexus 6 for just $100, so long as they bought the phone from Google during the Project Fi setup process. All it takes is a quick call, chat or email with Project Fi support, and you'll have a new phone shortly.
This follows in the footsteps of rather vague and unadvertised policies from the Play Store and Google Store that (seemingly on-and-off) offer free or discounted replacements for Nexus devices, but this one is hardly vague — Project Fi offers any customer who bought a Nexus 6 through Fi a one-time $100 replacement within a year of purchase, with no questions asked.
Sure it's not quite as good as a free replacement (like what you'd get with a manufacturer defect), but having the opportunity to swap out your broken $500 Nexus 6 for a new one for just $100 is a pretty great deal. Considering that this is a one-time offer and there's a fee involved you probably won't want to use it for things like scratches and dings (as I recently ran into on my own Nexus 6), and should probably wait for something like a screen crack or water damage.
But of course if your Project Fi Nexus 6 is looking a little tired after, say, 11 months of use, it may not be a bad idea to get a fresh one before the one-year policy runs out for just $100. It isn't as big and advertised as other insurance plans — like those from HTC, Motorola and others — but knowing it's there is fantastic. Still, maybe you should consider using that swanky Project Fi case that came with your phone to mitigate the damage in the first place.