By default, the Migration Agent for Exchange (MAgE) Unified Calendar Sync Agent does not synchronize Free / Busy data from Target to Source for switched users, or when configured for a two-way synchronization.
This should only impact users that are using Outlook 2007 and earlier versions in the Source Exchange environment.
To validate the state of the LegacyFreeBusySync switch - the following log line is seen in the MAgE Unified Calendar Sync Agent log:
2015-12-15 23:18:07.6700 Px23B4 Tx2A A2 C21 M8 Trace LegacyFreeBusySync: 'False'.
To resolve this issue, simply set the LegacyFreeBusySync switch to 'True' by using the DMMExPowerShell module. More information on how to use the DMMExPowerShell module can be found at the following link: