Editing XCOM: At Any Cost (section)

====Action-Based Resolution (p. 24)====
Using this mod, anything a player character or GMC does is called an action. If you want to carry out an action, you declare it, gather up your pool, and roll the dice, just as if you were starting a contest. Instead of moving to a back and forth escalation like a contest, the action is opposed by a reaction, which is either the target of the action rolling their own dice, or a difficulty set by the GM rolling difficulty dice. If the reaction beats the action’s total, the action fails.

Because the action’s dice are always rolled first, before difficulty dice or opposing reactions are rolled, action-based resolution can make actions seem chancy. ''Players may not know whether they should include more dice into their totals with PP.'' '''To offset this somewhat, the GM’s difficulty total or the reaction total must exceed the action’s total for the action to fail.''' 

Even though we're not using the italicized section quoted above (I'll explain in-game), we are using the bolded section. Ties go to the aggressor in Action-Based Resolution.