For me it's logical that if solider checks motion scanner and detect the enemy that should reduce a surprise effect of detected opponents.
If soldier uses the motion scanner:
1) Check if x-com operative is confused by detected movement of other x-com operatives. If confused, no reaction bonus (may be we can reduce reaction if too confused) and mutual surprise remains.
2) Otherwise if x-com operative is fully sure that is a movement of an enemy, that will disable mutual surprise for that detected unit and increase reaction versus that unit.
3) Next turn will revert the surprise effect, so you need to scan again.
