Anybody who has ever tried to reconcile email logs from various sources will know it's an almost impossible task. The log formats depend on the software used, time fields are in many formats and sometimes do not include the year (even worse, different sites may or may not use accurate time sources or record their time zone.) Not even host names may be in a useful format for direct comparison.

It's a mess.

The government will waste a lot of money obtaining lousy data that can be challenged in many ways by any half competent lawyer.