Thanks for the question. For people curious about what a CMO-S is, please see an earlier post of mine here.
A surrogate conditioned motivating operation (CMO-S) may be linked to a consequence that is negative reinforcement, but it itself is not a form of negative reinforcement. CMOs are antecedent conditions before the behaviour is displayed; whereas, negative reinforcement is the effect that occurs after the behaviour.
CMOs that are aversive/unpleasant are linked to negative reinforcement. They are the conditions from which we want to escape from. This makes escape more valuable and therefore, escape-related behaviours more likely to occur/increase.