I did that and the game refused to launch because it said that the ability tag wasn't enuemerated. I used another techtree ability and ability requiring techs as templates, matched all the values, gave unique identifiers to both sides, and it didn't work.
<RaceTrait>
<InternalName>ImperiumAbility</InternalName>
<DisplayName>ImperiumAbility_Name</DisplayName>
<DisplayNameShort>ImperiumAbility_ShortName</DisplayNameShort>
<Description>ImperiumAbility_Dec</Description>
<IsAbility>1</IsAbility>
<Mod>
<EffectType>ImperiumAbility</EffectType>
<Target>
<TargetType>Faction</TargetType>
</Target>
<BonusType>Flat</BonusType>
<Value>1</Value>
</Mod>
</RaceTrait>
<Tech>
<InternalName>MasterImperiumTechs</InternalName>
<GenericName>ImperiumTechs</GenericName>
<DisplayName>ImperiumTechs_Name</DisplayName>
<TechTree>Master_Tree</TechTree>
<ShortDescription>ImperiumTechs_ShortDec</ShortDescription>
<Description>ImperiumTechs_Dec</Description>
<ColorDef>TechPurple</ColorDef>
<Icon>GC3_Colonization_Icon.png</Icon>
<Bink>GC3_Colonization_Temp.bk2</Bink>
<ResearchCost>48</ResearchCost>
<TechPoints>1</TechPoints>
<AICategoryWeight>
<Military>1</Military>
<Growth>1</Growth>
<Tech>1</Tech>
<Diplomacy>1</Diplomacy>
<Expansion>1</Expansion>
<Wealth>1</Wealth>
<Influence>1</Influence>
<Fortification>1</Fortification>
</AICategoryWeight>
<Prerequ>
<Techs>
<Option>EnvironmentalEngineering</Option>
</Techs>
<RaceTrait>
<Option>ImperiumAbility</Option>
</RaceTrait>
<TechAge>
<Option>AgeOfExpansion</Option>
</TechAge>
</Prerequ>
</Tech>