I have a question. Player A is traitor and he is in t room. He teleports out of the t room . Player B seen when player A was spawned outside the t room. Can player B kill player A?
Yes, assuming that the teleport location is not shared with other teleporters (such as the teleport location on bowling where the secret knife teleports you to the same position as the T room does) you may kill someone for teleporting out of the T room. You just need to be able to prove that they were being teleported out of the T room is all.
Map knowledge. If you know for a fact that the teleport exit is only serviced by a T-room teleporter entrance, you may kill that player. If that teleporter exit is shared by other non-traitor room entrances, you may not.
If it's a t only teleport point, then yes, if there was any other way they could've spawned there without being in t room no.