A long time ago TP was in URF and I'm pretty sure they took it out because of the cannon. Which works really well, however recently I've had a lot of URF games where TP could be really useful.
Perhaps your split pushing and need to TP to dragon/baron with you team, or want to TP behind people where the cannon cant reach to gank them. Right now you would have to back and then get into the cannon, and someone might cancel that back. Also the cannon shows your location, and your vulnerable as you fall, where as a TP doesn't.
Additionally you can use TP to save yourself from being killed under tower by TPing back to base. I've seen Tryn as well as Akali do this. There are a number of champions that take barrier or heal just because they don't really have anything else to take, they would be able to take TP and get around the map better.(Illaoai is a good example here)
Over all I think there are some really awesome plays that could be made with TP and would love to see it readded.