When the ref sent Tansey off, he quite clearly indicates the elbow as making contact with samarass, as the reason for the red card.
You can't be sent off for looking at a player before a challenge, or for leading with arms(keepers would be sent off at corners all the time) as you need to use arms to help with a good leap at the ball. As seen in some scientific programme I watched recently, with Ronaldo, which proved that players gain a massive improvement in height when using arms to jump.
So once the ref looks at all the pictures and video's, he HAS to change his decision. He already looks like a fool, his only chance of recovering any respect is to admit he got it wrong!