This feature will be added in the next release of FOP2 I believe. Auto answer headers in FOP2 used to only work with originate actions not redirect actions, such as "call pickup" and "pickup from park".
If you want auto answer when picking up from queue, you need to add some custom dialplan in extensions_custom.conf. I can show you if you still need it.
I wanted the same thing as you, and the FOP2 developer helped me accomplish it. I believe he will add it in the next release, FOP2 2.30.05.