I have had the opposite experience with this device. I was able to pull a local IPv6 address on my MiFi 4510L. However, I have never been able to successfully detect and use a public IPv6 address. The same was true for the newer MiFi 4620L.
Public IP Address check:
That being said I have not checked up on this issue in a while. Perhaps something has changed that I am not aware of.
You need to have your OS configured correctly to recieve and accept IPv6 addresses. Once you complete the steps the MiFi will provide a local IPv6 address the next time you connect. I'll share some screenshots if I can find the time to get everything set back up again.
There are many tricks and techniques but I prefer the MS Fixit utilities for quickly enabling/disabling IPv6 on my Win7 laptop:
The fe80:: address is a link-local address. It did not come from your mifi. It's automatically supplied by the interface itself due to the fact that your operating system is IPv6-aware.
Thanks for clearing that up Nsayer. I supposed I never cared to look into it before and assumed it was working.
Now that you brought this to my attention I can see that the IPv6 address that I pulled is essentially the same as a 169.254.x.x IPv4 address. Fe80:: is not routable and not useful for anything other than maintaining the standards of the protocol. What a bummer, I had thought my local traffic was working over IPv6 this entire time : (