Sorry if I wasn't clear, in the method I'm describing each engineer is tracking and forecasting their own capacity one week at a time. We discuss it briefly as

Sorry if I wasn't clear, in the method I'm describing each engineer is tracking and forecasting their own capacity one week at a time. We discuss it briefly as a team to gut-check each other's forecasts and learn from misses as a group. Misses are almost always unexpected interrupts, so talking about what did we fail to see last week and then checking what might we be missing in the plan for this week is the essence of the whole thing. Having never done XP I can't say if the differences are better, I can only say that this basic approach works pretty well :)