The combination of power line communications (PLC) and radio frequency (RF) is essential for implementing new applications in smart grid and vehicular communications. In this paper, we propose a non-orthogonal multiple access (NOMA) based dual-hop hybrid wireless-power line communication (PLC) system with a decode-and-forward relay. The wireless channel is characterized by Nakagami-m fading under an additive white Gaussian noise, while the PLC channel is characterized by a Log-normal distribution with Bernoulli Gaussian noise including both background and impulsive noise components. New closedform expressions for the outage probability, and the asymptotic outage probability are derived under the practical assumption of imperfect successive interference cancellation (SIC) and verified via extensive representative simulations. For more insights on the outage performance, we also analyze the diversity order. Additionally, we proposed a power allocation optimization technique to achieve outage-optimal performance. The results show that the system outage probability improves as the arrival probability of the PLC impulsive component decreases. Finally, to highlight the achievable performance gain, the performance of the proposed system is compared against a benchmark OMA-based system.