Like in SCCM 2007, there is no option to monitor OS deployment in SCCM 2012, but we can create a custom status message query to view the status of OD deployment.
Below query will help to monitor OS deployment,
select stat.*, ins.*, att1.*, att1.AttributeTime from SMS_StatusMessage as stat left join SMS_StatMsgInsStrings as ins on ins.RecordID = stat.RecordID left join SMS_StatMsgAttributes as att1 on att1.RecordID = stat.RecordID inner join SMS_StatMsgAttributes as att2 on att2.RecordID = stat.RecordID where att2.AttributeID = 401 and att2.AttributeValue = "Deployment ID" and stat.SiteCode = "Site Code" and att2.AttributeTime >= ##PRM:SMS_StatMsgAttributes.AttributeTime## order by att1.AttributeTime DESC