What about users on cgnat? I know isp's in the far east that only offer cgnat and it's pot lock how you go out.
Other information,: Happy Eyeballs.
iOS 9 has a new feature called "Wi-Fi Assist" that will "automatically use cellular data when Wi-Fi connectivity is poor".
This will most likely cause those pesky IP checks to fail (even if you use a /24 or AS check). Geolocation checks will also fail in some cases.
My geolocation when connected to WiFi and when using cellular data are widely different. WiFi reports the city I'm in while cellular reports the city that their HQ is in.
that really depends on the carrier though, I suspect...
geo-ip stuff is so fun! and so often so wrong 