Basically create 4 different regions, where ever you need them to be. Then, I believe you have to:
Actions:
Set RandomRegions (Variable, Array) to Region 1
Set RandomRegions (Variable, Array) to Region 2
Set RandomRegions (Variable, Array) to Region 3
Set RandomRegions (Variable, Array) to Region 4
Now for the casting Trigger:
Events:
Unit casts an ability.
Conditions:
Ability (being cast) = Teleport
Actions:
Move unit instantly to RandomRegions(Random number between 1 and 4).
If they choose, then look for a dialog box tutorial.