Active Directory and FileVault
In our work environment, I have our Macs bind directly to Active Directory with no service (like QAS) in the middle. The AD user has a local home folder, we do not use Network Homes. We use FileVault 2 with no issues. The AD user's name shows up on the FileVault screen and they are able to unencrypt their laptop with their normal network credentials. So yes, it should work fine unless QAS is adding something bizarre into the mix.