In testing, everything worked great for us. After that phase, we rolled it to a couple users in production and now all machines including our test ones don't work so great.
I take a machine that is bound to our AD domain and add a 802.1x profile so that the device connects via Wi-FI adapter. This works great. I then enable "create a mobile account at login" and logout. I login as an administrative AD user, and as expected the Mac creates a local account. I then enable file-vault and reboot.
At this point, the Mac sits at the un-encrypt login prompt (as is normal for a FV machine) with the AD user I just created the mobile account for. I authenticate, and the machine begins to boot. Once I get to the user's desktop, I am not connected to my 802.1x specified network, and as such I'm not connected as an AD user. My local user no longer has admin privileges (since it is derived from AD group membership). To make it work, I logout from this failed session (not rebooting), and wait a minute. After this point, I re-authenticate as the same AD user and now I'm connected to my Wi-Fi network as per my 802.1x profile, and have all my AD related stuff including shares.
My 802.1x profile is configured with certificates, my 802.1x network SSID, and is set to authenticate to this network as the user at the login window.
What seems to be happening is that the Mac has my AD user/pass locally stored (obvious since it unlocks the disk). At some point during bootup, the Mac enables the Wi-Fi adapter, but is either tossing the 802.1x profile aside since the profile is configured to work at the login-window, or it is failing and skipping since the Wi-Fi adapter is being enabled during the un-encryption phase at which point the user is already logged in for.
Even without FV, this would seem to be an issue where the machine will boot up to a login window and if the user tries to authenticate with an account that exists as a mobile user on this box, the Mac may allow them to login as the local user if the network isn't ready yet. Alternatively, if the user booted the Mac and paused at the login prompt to allow the network to catch up, their AD credentials might work for them instead.
I don't see any reliable way to distinguish if the user will login as a network user or a local user in this scenario. Is there a way to introduce a delay or reconfigure the 802.1x profile in the FV scenario so that the Wi-Fi will attempt to connect to my specified SSID with the currently logged in user? If that isn't possible, is there a way to have an AD user with mobile account login to a FV enabled machine and connect to a 802.1x network (and be logged in as an AD user) without having to logout/login again after unlocking the disk? Is it possible for a FV enabled machine to allow a user to unlock the disk and simultaneously connect to a network (Wi-Fi or ethernet) as an AD user?