𝒻𝒟=OrderDistribution[CopulaDistribution[{"FGM",α},{ExponentialDistribution[1/(Subscript[τ, 1])],ExponentialDistribution[1/(Subscript[τ, 2])],ExponentialDistribution[1/(Subscript[τ, 3])]}],2];

sf[t_]=Refine[SurvivalFunction[𝒻𝒟,t],t>0]//Simplify

mtf=(Mean[𝒻𝒟]//Simplify)

Plot[sf[t]/.{(Subscript[τ, 1])->8.0,(Subscript[τ, 2])->5,(Subscript[τ, 3])->4.5}/.{{α->-0.9},{α->0},{α->0.9}},{t,0,8},Evaluated->True]