QueueMetrics supports Asterisk 1.6 - of course not through the AgentCallBackLogin command (that is just not there, go ask Digium) but through AddMember.
I know AddMember is not a perfect replacement for AgentCallBackLogin, so we made things easier by making available a multiple login on the Agent's page - this way your agents do not have to manually join or leave a number of different queues.
The main reporting and real-time engine works as fine with Addmember as with AgentCallbackLogin.