If he has applied thro PROPER CHANNEL , THEN HE HAS TO TECHNICALLY RESIGN .
Ask him to make sure his Lien in Parent Deptt is not terminated.
His service will be carried forward for PENSION PURPOSES ONLY.
His last pay drwan or increments WILL NOT BE CARRIED FORWARD as its a fresh appointment .
Further its a case of APPOINTMENT AFTER SUCCESSFUL TRAINING' . Whatever is due in Trg as per the New Deptt will be paid .
But keep his lien Active , in case not successful in Trg , can be reverted back to join his parent Deptt .