This paper investigates high-speed narrowband PLC MAC mechanisms attempting to satisfy utilities requirements for smart grid applications. Three protocols currently under discussion by different standardization bodies are studied: 1) ADaPtive backoff (ADP), a variation of the backoff protocol described in [1]); 2) G3 Binary Exponential Backoff (BEB) protocol ([3]); and 3) a variation of BEB denoted as Additive Decrease-Multiplicative Increase (ADMI). Aggregate and individual node throughput, long- and short-term fairness and excessive delays were analyzed under fully connected and traffic saturation conditions. In partially connected topologies, the effect of hidden node collisions and spatial reuse potential was studied.