Supporting Public Protection and Disaster Relief (PPDR) services are mandatory in modern wireless access networks. The sub-1GHz band is particularly suited to provide PPDR services due to the better propagation characteristics and attendant increase in link budget. In this work, we describe a novel transmit mode under a multi-operator non-orthogonal spectrum sharing framework, which can provide robust PPDR waveforms. This Ultra-Reliable Broadcast (URB) solution is based on the Licensed Shared Simultaneous Access (LSSA) broadband wireless access system which has been designed earlier by our group to provide much higher sum-rates in each cell when compared to a single-operator network, by enabling synchronization and different levels of co-operation across multiple TDD operators simultaneously using the same air-interface technology in the same spectrum. Using 19-cell system simulation with appropriate fractional frequency reuse scenarios, we compare the post-processing SINR CDFs of the 4 operator LSSA network and a single operator network, when both of these broadcast a single network-wide PPDR message. Their performances are also compared under disaster conditions where with a probability p, any of the eNodeBs can suddenly fail. We develop and use a simple 3-D stochastic path-loss model to account for users in multi-storey buildings, where depending on the user location the mean value of the shadow loss is varied. Our simulation results in the UHF band (500MHz carrier frequency) indicate that at the 10th percentile of the CDF, under normal operating conditions, the proposed URB solution with four LSSA operators can provide more than 10dB gain in SINR, and for p=0.5, this gain increases to 14dB, when compared to the single operator system. © 2017 IEEE.