I received my invite to Project Fi today and was about to jump onto the bandwagon but after some research, it looks like I won't be able to duplicate my current setup. I give out my carrier (AT&T) number to family/friends and my GV number for work/spam. I am able to have both numbers all routed through my phone's dialer and hangouts seamlessly. My plan was to transfer my GV number to another Google account and port my carrier number to Fi. However, I just found out that I will not be able to forward calls from my GV number to Fi or the other way around either.
https://support.google.com/fi/answer/6159953?hl=en
Bottom line, I won't be able to access both numbers on my phone once I join Fi. Unless I'm missing something that would enable this...?
Your situation sounds somewhat similar to mine.
Ultimately, I had to pass on Fi because I couldn't use the GV app and because Fi doesn't have conditional call forwarding.
I want to port the cell number from T-Mobile to the Google account to be used for Fi. That account does not have, and never has had, a GV number. I want to keep using a GV number that's on a separate account used for business, which is how it's been for years.
IOW needed to know if Fi will function as a straight-up replacement for T-Mobile postpaid service. Which means Fi must have conditional call forwarding. And since the GV number to be used is on a separate Google account, Fi must work with the GV app and VoiceChoice 2.0 the same way T-Mobile does. So, for Fi work as smoothly and easily as T-Mobile does now, Fi absolutely must be able to use the GV app.
It works like this: The GV app is set to make all calls through GV by default. But VoiceChoice 2.0 dials out, automatically choosing to use either the cell number or GV, depending on the contact group the contact being called is in. Business contacts see the GV business number, friends and family see the cell number. All calls to the GV number are forwarded to the cell number. Unanswered calls to the cell number are forwarded by conditional call forwarding back to GV so GV can handle all voicemail.
This works perfectly. Routing is automatic. You don't have to do anything special or remember anything, just uses the phone normally and GV and VoiceChoice 2.0 deals with which phone number is used for outgoing calls. Voicemail is centralized in one place and it even sends text transcriptions of voicemail. But if Fi can't use the GV app it loses all that super-handy functionality. And you need conditional call forwarding.
Android since v1.0. Linux user since 2001.