I can envision the problem to which you refer, and I agree that it may be worth proactively solving. (Proactive solutions involve governance/political capital/stakeholder management. In some environments, political capital and governance are extraordinarily expensive, so it may actually be long run cheaper to plan for failure and solve the problem retroactively).
On the face of it, this is either a quality problem or a risk problem. Team A feeds Team B; Team B needs to express the desired quality standards, and team B needs to plan to mitigate the risks if the quality standards are not met. As @David Espina says, if you're not managing (intra team) requirements, you're not managing the work. If we're talking protocols, inputs and outputs, then the common desire for an excellent result compells us to share very detailed information about expectations.
Does that involve a formal SLA for the teams? That depends on the relationships involved. If the teams are close and cooperative, then a formal SLA may actually inhibit innovation and improved quality. I get nervous when you introduce the term "forced to", because I think the cooperation is probably more important than the actual quality of any part. If you don't have the intent to cooperate and to make each other look excellent, then you may have an XY problem, but perhaps I'm reading too deeply there.
Fortunately, given system decomposition we would not have to have 20 contracts. It would be like 5.
– LetMeSOThat4U Dec 20 '12 at 18:07