Accessing my old FileVault2 encrypted drive from my new SSD
In short, yes. I've just done a similar install, with the old, FileVault 2-encrypted volume on an external drive. When your new OS attempts to mount the encrypted partition, it will request a password. Entering the FV key will allow it to decrypt and mount the drive - I believe you can elect to save the key to your Keychain to avoid having to re-enter the password the next time it mounts.