Scrambled coordinates and reinforcements step

[Thaelion Hexis]

This is mainly in the context of Alpha Legion's scrambled coordinates. The strategem states: "Use this strategem at the start of the reinforcements step..." 

Does this step always occur, like a phase, regardless of whether or not my opponent is going to bring in reinforcements this turn, or is it only triggered when reinforcements are being brought in? 

 

Essentially do I play it when my opponent says they are bringing something in or do you have to risk wasting the CP and the opponent waiting a turn? 

[Xenith]

The phase always happens, even if nothing actually happens in it, like choosing not to move or charge in the charge phase. 

I guess you scramble coordinates then you opponent has to decide whether to bring stuff on. Leaving them off is a big gamble also, as they'll have wasted 40% of the units capabilities over the game.