Simplified mathematical formula or model needed to demonstrate Tit for Tat pricing

If industries are engaging in a tit for tat strategy how would an observer/analyst "prove" it?  Is there a model or mathematical formula (that's easy to follow?)

I am comparing tit for tat pricing strategy between Ford and GM

I have the success factors and Prisoner's Dilemma context setting.

I only need a model or math formula that "proves" tit for tat pricing.  Is there such a thing?