When another model has been activated (with this mutation, it doesn't matter what the action was) or after a zone card has activated against him (a threat to the model), you may use this mutation as a response to what that model (or zone card) just did (that would be the narrative for it. Technically, it just allows you to move up to medium distance and then choose the next (1-3) action tokens. This last part may not always be useful, so you may skip that part sometimes (e.g. there might be only opponent action tokens in the cup left for example).
The model with telepathy can of course use this again during another model's activation, but remember that you can only have 5 MP and this reflex mutation doesn't give you any MPs. Also it is a regular movement and as such it can by itself trigger overwatch fire, free melee attack if he by this move is disengaging someone, etc.
So, yes, the mutation can be useful to get some extra movement to get out of the way or to reach an artifact before an enemy does and sometimes choosing what model will activate next can be useful.
thank you, that helps a lot.
where is the rule that you can only have 5 mp???
I can only find a rule about using max 3 mp. except when it says otherwise on cards.