operational compliance versus controlled group testing?

Suppose we have three members of a controlled group cos X,Y and Z. All three have a standardized prototype profit sharing plan; the adoption agreement states that all employers participate in the plan . Each plan has a different allocation formula, one is prorata, the other fixed and the third integrated. Can each employer X,Y and Z allocate a discretionary amount  to just its employees based on its plan's allocation formula and then general test all the employees together for coverage and nondiscrimination?

I think your testing is sound but they are not following the terms of the plan docs.  Amend them to Non-Std or VS docs and properly exclude each entity the other plans. 

Exactly, you have three plans with all employees in all three plans. Whether X, Y or Z can declare and allocate a PS contribution to their intended plan only depends on the terms of the respective plans.