asterisk users - Jun 2010 - Getting ANI on UK BT ISDN - Is SS& required?

Does anyone know if ANI is supported in the standard version of libpri?
We are currently running the latest asterisk 1.4 but with an older 
version of zaptel.

ANI seems to be supported in asterisk 1.4 in that least it is one of the 
variables within callerid but would I need to upgrade to the latest 
dahdi, upgrade dahdi and switch to asterisk 1.6 or even switch to the 
latest everything and use SS7 signaling?

Thanks
Gareth