Looks like it's possible, quoting from a similar thread on Reddit -
- Have a North American Nexus device (Fi won't work with euro devices,
re: network bands, CDMA support)
- Have a valid US address and bank account.
- Have a US Google account.
I'm not sure if the 2nd requirement
is actually a requirement(it is also moot because a sufficiently motivated tourist can open a US Bank Account), here are the acceptable payment methods(both credit and debit) -
- Visa
- MasterCard
- American Express
- Discover
However the first point is really important. Project Fi only works with certain devices.
These Nexus and Pixel models are unsupported, be sure to check this if your's isn't a North American model -
- Pixel Model G-2PW4200 (Rest of world version)
- Pixel XL Model G-2PW2200 (Rest of world version)
- Nexus 5X Model LGH791 and LGH791F
(Rest of world versions)
- Nexus 6P Model H1512 (Rest of world version)
- Nexus 6 Model XT1100 (Rest of world version)